fundamentals of gis review: nr 143 final exam ------using gis-- final exam: monday, may 7 10:30-1:15...
TRANSCRIPT
Fundamentals of GIS
Review:NR 143 Final Exam
------Using GIS--
Final Exam: Monday, May 7
10:30-1:15
110 Aiken
Closed book/notes
Fundamentals of GIS
Topics and format
Review of some important, post-midterm material follows.Don’t forget to study spatial reference and data structures!
question topic number points percent
Remote Sensing 10 46 23.0%
Raster Analysis 7 34 19.0%
Public Data 5 23 11.5%
Spatial Reference 3 21 10.5%
Geocoding 3 19 9.5%
Metadata 2 14 7.0%
Data Quality (error) 3 13 6.5%
GPS 3 13 6.5%
TIN 2 9 4.5%
Data Structures 2 8 4.0%
40 200 100.0%
question type
short answer 17 80 40.0%
medium answer 5 40 20.0%
multiple choice 20 80 40.0%
41 200 100.0%
Fundamentals of GIS
Topic detailRemote Sensing
Terms, sensor properties & types of resolution, comparison of sensors, classification techniques, electromagnetic spectrum, spectral response curves….
Raster Analysis
Techniques and their purposes, surface tools, filters, viewshed….
Public Data
Acronyms, important datasets and what is included with each, compare….
Spatial Reference
Projection types, terms & concepts, compare, scale factor, PCS’s….
Geocoding
Components and purpose, different approaches and their result….
Lecture Materials by Austin Troy except where noted © 2008
Fundamentals of GIS
Topic detail continuedMetadata
Why metadata? Sections and components? Terms….
Data Quality (error)
Terms, error types, quantitative vs. qualitative data….
GPS
Satellite system terms, differential GPS, sources of error….
TIN
Purpose(s), creating a TIN, parameters, advantages….
Data Structures
Field types, storage unit characteristics….
Lecture Materials by Austin Troy except where noted © 2008
Fundamentals of GIS
Raster Analysis
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Fundamentals of GIS
Raster dataRaster Elements
–Extent
–# rows
–# columns
–Coordinates
–Origin
–Orientation
–Resolution
–Grid cell
Fundamentals of GIS
Reclassification with Grids
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Here we reclass to 3 classes, based on natural breaks
Fundamentals of GIS
Raster Analysis Overview• Raster overlay queries
– Example: [elevation > 2500] AND [slope > 20]
• Raster overlay calculations– Example: [soil_depth_1990] – [soil_depth_2000]
• Zonal Statistics
• Raster terrain functions (hillshade, slope, aspect, contours)
• Viewshed AnalysisTerrain + Points = Visibility raster
• Neighborhood Statistics & Filters
• Distance Functions & Density
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Raster calculator
Local * Focal * zonal * global
Fundamentals of GIS
Lecture Materials by Austin Troy except where noted © 2008
Viewshed analysisInputs/outputs? Parameters?
In this case, red is for tower 1, blue for 2 and green for 3
Fundamentals of GIS
Lecture Materials by Austin Troy except where noted © 2008
Raster terrain functions in ArcGISHillshade: Slope: Contours: Aspect:
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Illumination / brightness values
Rise / run expressed as percent slope OR as angle (degrees)
Azimuth angle of steepest path (orientation or bearing of the slope direction)
User-defined interval and base contour
Fundamentals of GIS
Zonal Statistics• Summarize the mean, max
or sum for some value within each of the bounding units
• Polygon and Raster• Raster and Raster• Here we summarize by
subdivision zones the mean soil erodibility value (from our calculation).
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Lecture Materials by Austin Troy, Brian Voigt and Weiqi Zhou except where noted © 2011
Fundamentals of GIS
Neighborhood Statistics (Focal)• A method of summarizing raster data within a neighborhood by a
statistical measure, like mean, std dev.
– Neighborhood shape
– Neighborhood settings
• Window size
• Units
– Statistic types
Fundamentals of GIS
Neighborhood FiltersFilter types
– Low pass filters – remove noise (emphasize trends)
– High pass filters – edge enhancement (emphasize local detail)
Fundamentals of GIS
Distance Analysis
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Used to answer questions related to distance
– Proximity
– Straight Line Distance Measurement
– Cost Weighted Distance Measurement
– Shortest Path
Fundamentals of GIS
Density Functions• Use sample points to create density surfaces
• Can use a z value, or it can simply be based on the abundance and distribution of points.
• Output: number of points per unit area of a designated neighborhood
Fundamentals of GIS
Terrain Analysis
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Fundamentals of GIS
• Raster slope is calculated by steepest path in neighborhood• Aspect is direction of steepest path (azimuth in degrees)• Critical for flow path analysis, watershed generation, drainage network and viewshed analysis, etc.• Contour generation
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Slope, Aspect, Contours55 51 48
54 43 36
53 45 38
Fundamentals of GIS
• Triangulated Irregular Network• Irregular distribution of
elevation sample points• Breaklines• Z-tolerance (~resolution)• Delauney triangulation
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Three Dimensional data — TIN
Fundamentals of GIS
• 3D visualization• Extrude a third dimension• Drape thematic layers on elevation• Create animations (fly-through)
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ArcScene
Fundamentals of GIS
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3D Visualization
Fundamentals of GIS
Public Data
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Fundamentals of GIS
GIS Data• Acronyms!
• What’s included? How do they compare? Scale?• USGS National Map
SRTM
NHD
DEMNED
DOQDLGNWIGNIS
NLCD
DRG
7.5 minute
30m resolution
1/3 arc second
HypsographyImperviousness
hydrography NAIP
CLUSSURGO
TIGER
Fundamentals of GIS
The difference between an aerial photograph and an orthophoto
• Aerial photo– image displacement caused
by tilting of camera and terrain relief
– scale is not uniform
– cannot measure distances on a photograph
• Orthophoto– rectified to remove non-
constant scale due to varying distance to camera
– Also adjusts for elevation and tilt
– Therefore possible to measure distances directly like on other maps
– Can serve as a base map onto which other info may be overlaid
Light travels longer distance at scene edge: magnification
Fundamentals of GIS
Geocoding & Digitizing
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Fundamentals of GIS
What is Geocoding?• Convert lists/spreadsheets to features (needs a mechanism to calculate coordinates for the address) • Address matching: uses street address database, created from a streets layer
Address table + reference layer = point features• Reference layer defined in ArcCatalog as “address locator”• Takes advantage of ref. layer attributes & topology (left/right)• Geocoding accuracy = fn(reference layer accuracy)
Fundamentals of GIS
Geocoding example: 1060 Main Street
• Point is placed on even (upper) side of street• Position of 1060 is interpolated
Main St1000 1100
1001 1101
L-F-ADDR L-T-ADDR
R-F-ADDR R-T-ADDR
It looks for Main street, then for the 1000-1100 block
direction
1060 Main St
Fundamentals of GIS
Specify reference file
Specify address range attributes
Specify rules for address list
Specify zone
Geocoding in ArcGISTools >> Geocode addressesArcCatalog:
Fundamentals of GIS
Geocoding and Error
100 m
100 m
300 m
Fundamentals of GIS
Geocoding and Error
A rural area with a long road segment: very imprecise
An urban road segment: smaller, more precise
Rural street segments are also more subject to greater error because longer street segments means more interpolation
Fundamentals of GIS
XY GeocodingWe can also create points from a table by their latitude and longitudeDo this by clicking:
CA hazardous waste sites
• Then we specify the lat and long fields as well as the spatial reference system
• Lat and Long should be in decimal degrees
Fundamentals of GIS
Digitizing
• Tablet digitizing
• Heads-up digitizing
Often “drawing” features over an orthophoto base
Fundamentals of GIS
GPS
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Fundamentals of GIS
GPS• GPS (NAVSTAR): one of two GNSS – Global Navigation Satellite System…. GLONASS is the other…. more coming
• 30 NAVSTAR satellites; need at least 3 to determine location (better to have 4 or more)
r1
r2r3
Fundamentals of GIS
How Does GPS Work?
• We need at least 3 satellites as reference points (better to have 4 or more)
• Position is calculated using trilateration
Fundamentals of GIS
• Calculating range (distance from satellite to receiver)
• Time determined from lag in pseudo-random code, one from satellite and one generated at the same time by the receiver.
• 4th satellite helps with time synch
Source: Trimble Navigation Ltd.
How Does GPS Work?
Sent by satellite at time t0
Received from satellite at time t1
Distance = Velocity * Time
Fundamentals of GIS
Sources of Error• Gravitational effects
• Atmospheric effects
• Obstruction & Multipath
• Satellite geometry…. PDOP
• Selective Availability
Fundamentals of GIS
Locating Satellites
• Need to know satellite locations to determine geometry/PDOP
• Ephemeris and Almanac are part of transmitted signal
Fundamentals of GIS
How does DGPS work?• One stationary & one moving receiver …. error
• The stationary receiver must be located on a known control point …. Correction factor sent to rover
Fundamentals of GIS
Remote Sensing
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Fundamentals of GIS
Electromagnetic Radiation
• Electromagnetic Spectrum
Radiation Source
Irradiance
Wavelength(Micrometers)
Ultra-Violet
Visible Near IR Shortwave IR Midwave IR Longwave IR
Pan
chrom
atic F
ilm
Color Film
.01 .04 .07 1.0 3.0 5.0 14.00 um
Visible comprises 2%of EM Spectrum
Visible
Spectral ImageryIR Film
Fundamentals of GIS
Passive Detection
Camera or sensor
irradiancereflectancescattering
transmittanceabsorption
Fundamentals of GIS
Reflectance
High
Low
Blue Green Red
Ref
lect
ance
0.4m 0.5m 0.6m 0.7m
White LightGreenGreenBlueBlue
RedRed
Fundamentals of GIS
So, what are RS data?
• RS imagery is raster data.
• Each picture element (pixel) has a value, or digital number (DN).
Fundamentals of GIS
Spectral Response Curves50
40
30
20
10
0
0.4 0.6 0.7 0.8 1.3
Artificial turfAsphalt
Fallow field
Sandy loamy Soil
Concrete
REFLECTANCE
(%) Clear water
Wavelength (micrometers)
Grass
Visible0.5
GREENBLUE GREEN RED
Near IR
Fundamentals of GIS
Band Placement
Wavelength, m
Landsat TM
RGB
100
50
0
25
75
Per
cent
Re
flect
ance
Near IR Mid IR
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
Silty-clay soilTurbid river water
Vegetation Clear river waterMuck soil
1 2 3 4 5 7
visible
1 2 3 4MSI
IKONOS & HI RESPAN
LANDSAT 7 PAN
Fundamentals of GIS
Multispectral Display
BLUEBLUE
GREENGREEN
REDRED NEAR IR SHORT
WAVE IRMID-
WAVE IRLONGWAVE IR
1Landsat TM Band 2 3 4 5 7 6
Band Combination = 7 4 2 (LANDSAT)
Color Guns =
Band Composite Output =
Fundamentals of GIS
3-2-1 4-3-2 4-5-2
Landsat band combination comparisons
False color composite
Color infrared composite (CIR)
True (natural) color
composite
Fundamentals of GIS
Sensor Properties• Spatial resolution (pixel size)
• Spectral resolution (# bands)
• Radiometric resolution
• Temporal resolution
IKONOS 4mLandsat 30m
Orthophoto 0.5m
©
Space Imaging
100s of BandsHyper-spectral
Band 2
.53-.62
Band 3
.63-.69
Band 1.45-.52
Visible
Band 4
.79-.90
Band 5
1.55-1.75
Band 7
2.08-2.35
Band 6
10.4-12.4
Near IR SWIR LWIR
1000s of BandsUltra-spectral
Multi-spectral
– bit depth
– orbital period (return rate)
Fundamentals of GIS
Trade-offs
Spatial Resolution ½ m 4m 30m
# Bands 1 4 7
Radiometric Resolution
8 bit 11 bit 8 bit
Temporal Resolution On demand 3-4 days 16 days
Aerial Photo IKONOS Landsat
© Space Imaging
Compare also: SPOT, Quickbird, ASTER
Fundamentals of GIS
Active Sensors• IfSAR – Inferometric Synthetic
Aperture Radar
• LIDAR – LIght Detection And Ranging
received signal
transmitted signal
Fundamentals of GIS
Major Satellite Systems
• High spatial resolution
– Quickbird, IKONOS, OrbView-3, SPOT-5 PAN, IRS-P6
• Medium spatial resolution
– Landsat-5 TM, Landsat-7 ETM+, ASTER, SPOT
• Low spatial resolution
– MODIS, ENVISAT, GOES, AVHRR, MSS
Fundamentals of GIS
Orbits• Most of these satellites are in sun-synchronous orbit
• Satellite passes over the same part of the Earth at roughly the same local time each day
• ~8 degrees inclined from polar orbit, allowing match with earth’s rotation
• Maintains sun angle
Source: http://hdsn.eoc.nasda.go.jp/experience/rm_kiso/satellit_type_orbit_e.html
Fundamentals of GIS
Materials by Austin Troy and Weiqi Zhou except where noted © 2008
Scanners• Pushbroom (along track) vs. Whiskbroom (across track)
• LANDSAT (MSS, TM, ETM+)
• SPOT (HRV)
• IKONOS
• Compare resolution(s), other characteristics
• Off-nadir viewing
Source: http://www.sci-ctr.edu.sg/ssc/publication/remotesense/spot.htm
Fundamentals of GIS
Image Pre-Processing• Create a more faithful representation through:
– Geometric correction
– Radiometric correction
– Atmospheric correction
• Image enhancement
– Spatial feature manipulation: Spatial filtering, edge enhancement, and Fourier analysis…. Low-pass & high-pass filters
– Contrast manipulation: Gray-level thresholding, level slicing, and contrast stretching.
– Multi-image manipulation: Band ratioing, principal components, vegetation components, canonical components…. Orthophoto vs. “true” orthophoto
• Rectification – remove distortion (platform, sensor, earth, atmosphere) …. Scanned aerial photo vs. orthophoto
Fundamentals of GIS
Image classification
• Turn RS data into meaningful information (feature extraction)
• Spectral pattern recognition – supervised vs. unsupervised …. training sites
• Spatial pattern recognition
• Temporal pattern recognition
• Applications – land cover mapping (Anderson classification)
• Accuracy assessment
Fundamentals of GIS
Object-oriented classification: 3 Steps• Segmentation • Feature
extraction
• Classification
Fundamentals of GIS
Object-oriented Classification
BBBB
CCCC
Fundamentals of GIS
Data Quality & Documentation(Error & Metadata)
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Fundamentals of GIS
Data Quality• Accuracy + Precision = Quality
• Error = fn(accuracy, precision)
• Cost vs. quality tradeoff
• Random vs. Systematic error
• Positional accuracy
• Attribute accuracy & precision (quantitative vs. categorical)
SCALE
Which can be controlled?
Standards
Fundamentals of GIS
Other measures of data quality• Logical consistency
• Completeness
• Data currency/timeliness
• Accessibility
Common sources of error?
Fundamentals of GIS
Error ….• Accuracy & Precision
•Positional vs. Attribute Accuracy
•Propagation (single step)
• Cascading (multi-step)
• Cascading error can be managed to a certain extent by conducting “sensitivity analysis” Image source: http://oopslist.com/Conflation (2 types)• Attribute
• Feature
Fundamentals of GIS
Documentation and Metadata
• Purpose?
• Federal mandate…. FGDC (“Content Standard for Digital Geospatial Metadata”)
• Terminology!
Fundamentals of GIS
Documentation and MetadataSome roles/purposes of metadata:
1. Information retrieval, cataloguing, querying and searching for data electronically.
2. Describing fitness for use (applicability) and documenting the usability and quality of data.
3. Describing how to transfer, access or process data
4. Documenting all relevant characteristics of data needed to use it
5. Data permanence; creates institutional memory; advertises an organization’s research (generate partnerships)
Fundamentals of GIS
Materials by Austin Troy © 2008
Documentation and Metadata• Metadata usually include sections similar to these
Fundamentals of GIS
Documentation and MetadataCritical components usually break down into:
1. Dataset identification, overview
2. Data quality
3. Spatial reference information
4. Data definition
5. Administrative information (distribution)
6. Meta-metadata