![Page 1: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/1.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 2: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/2.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 3: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/3.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 4: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/4.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 5: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/5.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 6: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/6.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 7: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/7.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 8: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/8.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 9: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/9.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 10: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/10.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 11: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/11.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 12: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/12.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 13: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/13.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 14: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/14.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 15: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/15.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 16: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/16.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 17: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/17.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 18: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/18.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 19: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/19.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 20: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/20.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 21: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/21.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 22: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/22.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 23: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/23.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 24: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/24.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 25: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/25.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 26: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/26.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 27: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/27.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 28: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/28.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 29: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/29.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 30: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/30.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 31: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/31.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 32: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/32.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 33: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/33.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 34: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/34.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 35: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/35.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 36: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/36.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 37: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/37.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 38: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/38.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 39: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/39.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 40: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/40.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 41: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/41.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 42: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/42.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 43: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/43.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 44: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/44.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 45: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/45.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 46: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/46.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 47: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/47.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 48: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/48.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 49: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/49.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 50: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/50.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 51: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/51.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 52: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/52.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 53: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/53.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 54: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/54.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 55: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/55.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 56: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/56.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 57: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/57.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 58: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/58.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 59: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/59.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 60: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/60.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 61: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/61.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 62: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/62.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 63: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/63.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 64: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/64.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 65: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/65.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 66: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/66.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 67: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/67.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 68: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/68.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 69: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/69.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 70: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/70.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 71: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/71.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 72: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/72.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 73: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/73.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 74: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/74.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 75: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/75.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 76: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/76.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 77: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/77.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 78: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/78.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 79: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/79.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 80: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/80.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 81: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/81.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 82: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/82.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 83: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/83.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 84: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/84.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 85: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/85.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 86: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/86.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 87: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/87.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 88: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/88.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 89: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/89.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 90: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/90.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 91: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/91.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 92: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/92.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 93: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/93.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 94: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/94.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 95: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/95.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 96: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/96.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 97: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/97.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 98: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/98.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 99: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/99.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 100: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/100.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 101: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/101.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 102: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/102.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 103: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/103.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 104: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/104.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 105: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/105.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 106: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/106.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 107: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/107.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 108: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/108.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 109: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/109.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 110: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/110.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 111: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/111.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 112: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/112.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 113: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/113.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 114: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/114.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 115: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/115.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 116: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/116.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 117: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/117.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 118: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/118.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 119: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/119.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 120: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/120.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 121: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/121.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 122: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/122.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 123: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/123.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 124: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/124.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 125: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/125.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 126: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/126.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 127: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/127.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 128: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/128.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 129: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/129.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 130: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/130.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 131: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/131.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 132: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/132.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 133: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/133.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 134: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/134.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 135: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/135.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 136: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/136.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 137: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/137.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 138: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/138.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 139: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/139.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 140: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/140.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 141: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/141.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 142: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/142.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 143: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/143.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 144: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/144.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 145: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/145.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 146: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/146.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 147: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/147.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 148: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/148.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 149: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/149.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 150: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/150.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 151: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/151.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 152: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/152.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 153: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/153.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 154: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/154.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 155: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/155.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 156: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/156.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 157: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/157.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 158: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/158.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 159: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/159.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 160: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/160.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 161: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/161.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 162: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/162.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 163: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/163.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 164: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/164.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 165: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/165.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 166: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/166.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 167: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/167.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 168: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/168.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 169: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/169.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 170: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/170.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 171: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/171.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 172: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/172.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 173: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/173.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 174: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/174.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 175: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/175.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 176: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/176.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 177: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/177.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 178: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/178.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 179: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/179.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 180: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/180.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 181: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/181.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 182: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/182.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 183: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/183.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 184: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/184.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 185: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/185.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 186: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/186.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 187: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/187.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 188: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/188.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 189: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/189.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 190: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/190.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 191: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/191.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 192: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/192.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 193: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/193.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 194: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/194.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 195: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/195.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 196: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/196.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 197: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/197.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 198: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/198.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 199: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/199.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 200: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/200.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 201: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/201.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 202: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/202.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 203: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/203.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 204: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/204.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 205: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/205.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 206: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/206.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 207: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/207.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 208: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/208.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 209: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/209.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 210: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/210.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 211: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/211.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 212: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/212.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 213: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/213.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 214: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/214.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 215: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/215.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 216: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/216.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 217: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/217.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 218: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/218.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 219: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/219.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 220: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/220.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 221: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/221.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 222: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/222.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 223: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/223.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 224: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/224.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 225: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/225.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 226: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/226.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 227: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/227.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 228: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/228.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 229: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/229.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 230: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/230.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 231: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/231.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 232: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/232.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 233: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/233.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 234: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/234.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 235: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/235.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 236: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/236.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 237: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/237.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 238: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/238.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 239: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/239.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 240: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/240.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 241: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/241.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 242: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/242.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 243: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/243.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 244: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/244.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 245: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/245.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 246: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/246.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 247: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/247.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 248: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/248.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 249: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/249.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 250: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/250.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 251: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/251.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 252: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/252.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 253: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/253.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 254: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/254.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 255: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/255.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 256: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/256.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 257: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/257.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 258: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/258.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 259: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/259.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 260: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/260.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 261: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/261.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 262: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/262.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 263: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/263.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 264: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/264.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 265: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/265.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 266: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/266.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 267: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/267.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 268: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/268.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 269: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/269.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 270: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/270.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 271: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/271.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 272: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/272.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 273: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/273.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 274: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/274.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 275: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/275.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 276: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/276.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 277: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/277.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 278: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/278.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 279: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/279.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 280: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/280.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 281: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/281.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 282: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/282.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 283: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/283.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 284: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/284.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 285: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/285.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 286: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/286.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 287: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/287.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 288: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/288.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 289: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/289.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 290: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/290.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 291: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/291.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 292: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/292.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 293: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/293.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 294: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/294.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 295: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/295.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 296: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/296.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 297: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/297.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 298: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/298.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 299: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/299.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 300: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/300.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 301: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/301.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 302: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/302.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 303: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/303.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 304: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/304.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 305: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/305.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 306: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/306.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 307: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/307.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 308: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/308.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 309: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/309.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 310: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/310.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 311: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/311.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 312: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/312.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 313: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/313.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 314: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/314.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 315: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/315.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 316: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/316.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 317: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/317.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 318: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/318.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 319: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/319.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 320: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/320.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 321: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/321.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 322: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/322.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 323: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/323.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 324: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/324.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 325: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/325.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 326: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/326.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 327: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/327.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 328: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/328.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 329: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/329.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 330: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/330.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)
![Page 331: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/331.jpg)
1
Territories, Environment, Remote Sensing & Spatial Information Joint Research Unit Cemagref - CIRAD - ENGREF
Pierre BAZILE
GIS: concepts, methods & toolsGIS: concepts, methods & tools
METIER METIER GraduateGraduate Training Course no. 2 Training Course no. 2 –– Montpellier Montpellier -- FebruaryFebruary 20072007
Information Management in Information Management in EnvironmentalEnvironmental SciencesSciences
Introduction to GISIntroduction to GIS
Structuring of geographic informationStructuring of geographic information
![Page 332: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/332.jpg)
2 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
INFORMATION SYSTEM AND ORGANIZATIONINFORMATION SYSTEM AND ORGANIZATION
CONTROL SYSTEM
INFORMATION SYSTEM
Problem Decision
Requests Information
Inputs
Outputs
EXTERNAL
UNIVERSE
INFORMATION
BASE
STATIC
Data, rules, and
constraints of the
external universe
DYNAMIC
INFORMATION
PROCESSOR
Actions
Personnel
![Page 333: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/333.jpg)
3 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
AUTOMATIZATION OF THE INFORMATION SYSTEMAUTOMATIZATION OF THE INFORMATION SYSTEM
AUTOMATIZED INFORMATION SYSTEM
Inputs
Outputs
FORMALISABLE
UNIVERSE
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Data
model
Computer
Software: DBMS
(Database management system)
![Page 334: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/334.jpg)
4 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SPATIAL REFERENCE INFORMATION SYSTEMSPATIAL REFERENCE INFORMATION SYSTEM
INFORMATION SYSTEM
Inputs
Outputs
INFORMATION
BASE
STATIC DYNAMIC
INFORMATION
PROCESSOR
Personnel
Semantic
data
model
Software: GISSpatial
data
model
Software: DBMS
Computer
(Geographic infomation system)
![Page 335: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/335.jpg)
5 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GIS: WHAT EXACTLY IS IT?GIS: WHAT EXACTLY IS IT?
The term GIS represents, in fact, 3 different concepts:
• An information system about a territory or project
• The databases describing this IS
• The IT solutions used (in particular: software)
One has to return to the basic concept!
Importance of the spatial component of the IS (localization of objects and processes, spatial interactions between elements)
![Page 336: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/336.jpg)
6 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GEOGRAPHICAL DATAREPRESENTING GEOGRAPHICAL DATA
Duality of Geographical Information:
• Graphical information:The geographical objects, their localization, their topological relationships
• Thematic information:The descriptors of these objects, of these localizations
‘semantic’ data
500 Metres0
N
![Page 337: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/337.jpg)
7 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
REPRESENTING GRAPHIC DATAREPRESENTING GRAPHIC DATA
Semantic
database
Semantic
database
Entities
Relationship
Spatial
representation
Spatial
representation
Entities
Relationships
Point
Line
Surface
Continuous
Tables
Adjacency
Inclusion
Proximity
Path
Link
![Page 338: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/338.jpg)
8 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
CODING GEOMETRY : TWO MODESCODING GEOMETRY : TWO MODES
• image vs ‘line drawings’
• raster vs vector
![Page 339: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/339.jpg)
9 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATIONVECTOR REPRESENTATION
bâtiment
route
lac
![Page 340: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/340.jpg)
10 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
‘SPAGHETTI’‘SPAGHETTI’
Point: Id,x,y +
Line: Id,
x0,y0x1,y1x2,y2.--------
xn,yn
Surface: Id,
x0,y0x1,y1x2,y2--------
xn,yn(x0,y0)
1 2
1 2 3
4 5 6
P1 P2
x1,y1 x2,y2
x2,y2 x3,y3
x5,y5 x6,y6
x4,y4 x5,y5x1,y1 x2,y2
Data redundancy
Undefined relationships
![Page 341: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/341.jpg)
11 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION:VECTOR REPRESENTATION:
NETWORK TOPOLOGYNETWORK TOPOLOGY
Point: Id,x,y +
Line: Id, (L)
Nax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
1 2
1 2 3
4 5 6
No redundancy
Management of connectedness
L1 L2 L3
N1
N2
L1
N1x1,y1
x4,y4
N2
L2
N1N2
L3
N1x3,y3
x6,y6
N2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 342: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/342.jpg)
12 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR REPRESENTATION: VECTOR REPRESENTATION:
SURFACE TOPOLOGYSURFACE TOPOLOGY
1 2
1 2 3
4 5 6
Management of connectedness
Management of contiguity
Point: Id,x,y +
Line: Id, (L), Pg,PdNax1,y1x2,y2.--------
Nb
Node: Id,x,y
Surface: Id,
L1L2----
Ln
L1 L2 L3
N1
N2
L1
N1
N2
P1U
L2
N1
N2
P2P1
L3
N1
N2
U
P2
P1
L1
L2
P2
L2
L3
N1
x2,y2
N2
x5,y5
![Page 343: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/343.jpg)
13 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
‘SPAGHETTI’ MODEL‘SPAGHETTI’ MODEL
• Entities
– point: x, y coordinates
– line: list of x,y coordinates corresponding to nodes
– sometimes polygons: set of x,y coordinates, forming a loop: the first coordinate
couple = last coordinate couple
� The spaghetti mode produces a visual effect of polygons but, most often, no polygon
entity is stored
• No spatial relationships between objects– unjoined arcs – unclosed polygons
� polygons cannot form a surface
– intersections without nodes at the crossing of two arcs
– Adjacent polygons that overlap or separated by ‘blanks’
Appearence
!
Reality
![Page 344: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/344.jpg)
14 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
TOPOLOGICAL MODELTOPOLOGICAL MODEL
• Managing the connectedness and contiguity of objects
• 2 types of topology: – Planar topology
– Network topology
• Topological entities:– With permanent storage of the topology
• e.g.: ArcInfo coverage
– Taking into account only when editing (creating, updating); this data is called pseudo-topological.
• e.g.: shp (ArcView) or tab (MapInfo)
– With defined topological rules, varying depending on context
• e.g.: feature class within feature dataset in a geodatabase (ArcGIS)
![Page 345: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/345.jpg)
15 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK DESCRIPTIVE DATADBMS LINK DESCRIPTIVE DATA
Identifier Attributes of the surface
1
2
3
+1
+3+2
Identifier Attributes of the point
1
2
3
1
23
Identifier Attributes of the line
1
2
3
+1
+2
+3
LINK
Weak
Strong
Hybrid/Integrated
STRUCTURING
Layer -- Table
![Page 346: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/346.jpg)
16 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
extent
in Y or
rows
extent in X or columns
dx
dy
Size of the cell
(geometrical resolution)
Origin (X,Y)
N (orientation)
id attribute
1
2
3
Wheat
Grapevine
Forest
Identifier
RASTER PRESENTATIONRASTER PRESENTATION
![Page 347: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/347.jpg)
17 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DEPTHRASTER REPRESENTATION: IMAGE DEPTH
�Number of planes
�Depth of each planeboolean = 1 bit (21) 2 values: {0,1}byte = 8 bits (28) 256 values: {0,255}integer = 16 bits (216) 65536 values: {-32767,32765}...
Necessity of digital coding!
dz1
dz2
Thematic resolution
![Page 348: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/348.jpg)
18 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
1
1 1 1
1
2
2
2
2
3
3 3 3
3
RASTER REPRESENTATION: RASTER REPRESENTATION:
LINES AND POINTSLINES AND POINTS
1
2
3
The value chosen for the empty cell is selected by convention.
![Page 349: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/349.jpg)
19 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: RASTER REPRESENTATION:
CONTINUOUS DATACONTINUOUS DATA
11.4 11.5 11.6 11.8 11.9 12.2 12.5 12.4 12.212.0
11.4 11.6 11.7 11.9 11.9 12.4 12.6 12.6 12.412.0
11.5 11.7 11.8 11.9 12.4
11.7 11.9 12.0 12.5 12.6
11.8 12.1 12.4 12.5 12.8
12.0 12.2 12.5 12.7 12.9
12.5 12.5 12.8
12.6 12.6 12.4 12.111.9
13.0 13.1 12.6 12.312.1
13.0 13.2 12.7 12.412.0
13.4 13.6 13.1 12.712.4
13.7 13.9 13.6 13.212.613.1 13.2
Direct representation of the
variable
Associated data: statistical
summary
![Page 350: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/350.jpg)
20 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
DBMS LINK: DESCRIPTIVE DATADBMS LINK: DESCRIPTIVE DATAIdentifier Attributes of the
point
1
2
3
Identifier Attributes of the line
1
2
3
Identifier Attributes of the surface
1
2
3
LINK
Hybrid/integrated
STRUCTURING
Layer -- Table
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1
1 1 1 1 1
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 33 3
1
1 1 1
1
2
2
2
2
3
3 3 3
3
1
2
3
![Page 351: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/351.jpg)
21 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
RASTER REPRESENTATION: IMAGE DATARASTER REPRESENTATION: IMAGE DATA
Map (scanned)
Orthophotography
Digital Elevation Model
![Page 352: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/352.jpg)
22 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
FROM VECTOR TO RASTER: RASTERIZATION
FROM RASTER TO VECTOR: VECTORIZATION
VECTOR/RASTER CONVERSIONSVECTOR/RASTER CONVERSIONS
![Page 353: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/353.jpg)
23 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
VECTOR AND RASTER: VECTOR AND RASTER:
COMPLEMENTARITYCOMPLEMENTARITY• Raster:
– Grid of ‘independent’ cells
– Matrix calculations
– Redundancy – volume of information
• Vector:– Objects +- structured
– Information with low or no redundancy (depending on the structuring)
– Link with external databases
• Complementarity raster-vector
• Improvements in hardware architectures– Processor power / disk space
– Developments in raster solutions / image processing
![Page 354: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/354.jpg)
24 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
SCALE AND ACCURACY SCALE AND ACCURACY -- 11
• Definition:Constant ratio between lengths measured on the map and the
corresponding lengths measured on the land.
• Expression:– Algebraic expression = scale ratio
map at 1:25,000
– Graphical expression by a scale bar representing the ratio
Graphical expression of scale: INDISPENSABLE
• Semantic confusion
![Page 355: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/355.jpg)
25 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Significance of the scale:– Representation ratio
– Level of analysis of the studied phenomena
– Geometric accuracy of the information
• Level of approach of geographic space– Size of a zone representable at a given scale:
• A4 sheet: 600 km2 at 1:100,000
• … : 6 km2 at 1:10,000
– Level of analysis:
Compartment scale, regional scale, national scale
• Geometric accuracy of the information
SCALE AND ACCURACY SCALE AND ACCURACY -- 22
![Page 356: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/356.jpg)
26 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
• Scale = representation ratioAccuracy = quality of geometric information
• 2 dimensions of accuracy:– resolution = size of an ‘elementary’ pixel
– localization accuracy: localization error
• Scale/accuracy confusion: 2 causes– assumption of the reader: each point is significant
– assumption of the producer: no unnecessary quality
• With ‘undesirable’ consequencesthe zoom syndrome
SCALE AND ACCURACY SCALE AND ACCURACY -- 33
![Page 357: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/357.jpg)
27 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 11
Hardwares
Softwares
Methods
Users
Data
• Key-element of
any GIS project
• 70 to 80 % of
total project costs
![Page 358: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/358.jpg)
28 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 22
• Acquiring data from:– Institutional: public agencies
– Private providers
– External contractors
– Internal digitalization
GIS software incorporate tools to create layer:
– features digitalization,
– calculation on one or many existing plans,
– Image processing
![Page 359: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/359.jpg)
29 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
GEOGRAPHIC DATA QUALITY GEOGRAPHIC DATA QUALITY -- 33
• Which use ?– To use or extract information from this document
– As based map (illustration or filling)
– To take measurements
– To analyze simultaneously several information plans (spatial
analysis)
• Whatever use, consider :– Precision of imported data
– Level of detail
– Reference system used (compatibility with local database)
– Data property (copyright)
Information
to be stored
in metadata
![Page 360: · 2009-10-07 · 13/ 30 INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION ‘SPAGHETTI’ MODEL • Entities – point: x, y coordinates – line: list of x,y coordinates](https://reader036.vdocuments.mx/reader036/viewer/2022070705/5e9423bceb035663bf5c0282/html5/thumbnails/360.jpg)
30 / 30
INTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATIONINTRODUCTION TO GIS: STRUCTURING GEOGRAPHIC INFORMATION
METADATA, TO GUARANTEE DATA METADATA, TO GUARANTEE DATA
QUALITYQUALITY
• Metadata = "data about data"– The procedures followed to acquire the data
– The precision et methods of measurements
– The age of the data and update
– The data coding
– The geographic referencing
– The geometry
– The attributes
• Absence of metadata– False interpretation
– Bad usage
– Erroneous perception of precision
Example of metadata's appearance
ArcCatalog (ESRI)