introduction to geographic information
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Introduction to Geographic Information. Fall 2006 Instructor: Christine Erlien. Overview. What is geography? What is geographic information? How do we get it? What do we do with it? What is a GIS? Difference from CAC, CAD, analog mapping GIS applications Tool versus science. - PowerPoint PPT PresentationTRANSCRIPT
Introduction to Geographic Information
Fall 2006
Instructor: Christine Erlien
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Overview What is geography? What is geographic information?
How do we get it? What do we do with it?
What is a GIS? Difference from CAC, CAD, analog mapping
GIS applications Tool versus science
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Geography = Place names only?
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What is geography? The scientific study of the locational and spatial
variation in physical and human phenomena Where things are located on the earth’s surface
Why things are located where they are
How places differ from one another
How people interact with the environment
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Geographic Information Examining patterns & processes of human and
physical phenomena on the surface of earth
Examples of geographic information: Spatial distribution of world population totals or
growth rates Location of Chapel Hill Interstate I40’s spatial pattern Urban sprawl/development of Raleigh over time
http://sedac.ciesin.columbia.edu/gpw/
World Vegetation
http://www.miamisci.org/ecolinks/mapbiosphere.html
http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_plate_tectonics_world.html
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Geographic Information (GI)
GI - static or dynamic? Static: Does not change position
Benchmarks Locations, such as city/town, lake, park
Dynamic Car with On-Star recording its position Cell-phones used to track children’s locations Studying population change at a particular location
over time
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How do we obtain geographic information? Aerial photographs Digital remote sensing Surveying Censuses Global Positioning System Digitizing maps
11Aerial photograph from http://terraserver.microsoft.com
NC Satellite Image
www.geology.com
Surveying: benchmarks
Geodetic control points
Mark a point of known vertical elevation
Height calculated from height of nearby benchmarks
GPS receivers
Digitizing
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We’ve collected GI, now what do we do with it? Analyze the data
Make maps to present the data to others
How? By using a GIS
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GIS: Geographic Information Systems GIS is built on collective knowledge
Geography Cartography Computer science Mathematics
Many definitions, depending on whom you ask Demers (our textbook) cites Marble & Pequet
(1983), who talk about what we do with a GIS and how we do it
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Data: Both spatial and temporalSpatial: Related to the space around usTemporal: Related to time
The what and how of GIS:Data input subsystem: Collecting & preprocessing dataData storage & retrieval subsystem: Retrieval, updating, editingData manipulation & analysis subsystem: Analysis & modelingReporting subsystem: Display
What this boils down to: “GIS is an information system that allows for capture, storage, retrieval, analysis and display of spatial data.”
Marble and Pequet (1983)
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GIS
An information system that allows for Capture Storage Retrieval Analysis Display
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Computer hardware Software
Data management and analysis procedures
Spatial data People needed to operate the GIS
Components of a GIS
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The rise of GIS Canada, early 1960s, Dr. Roger Tomlinson Need: inventory & map natural resources A huge task, aided by advances in computing
technology Computers: vacuum tubes transistors
Faster, more reliable, cheaper Larger memories information storage as well as
calculations possible Mainframe used had 512K of memory!!!!
IBM develops the drum scanner to scan lines on maps –1st in the world
Interested in more history? Seehttp://www.casa.ucl.ac.uk/gistimeline/ for an interactive timeline
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How does GIS differ from CAC and CAD? Computer-aided cartography (CAC):
Primarily used in map-making (display) Examples
Global Mapper MapMaker ArcExplorer
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How does GIS differ from CAC and CAD? Computer-aided drafting (CAD)
Used by architects to produce graphic images (display)
Images not linked to descriptive files
What key capability of GIS is lacking in both CAC and CAD?
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Comparing traditional cartography & GIS: InputsTraditional Data sources
Aerial photography Digital remote sensing Survey Census & statistical
data Data recorded as
points, lines, areas on paper or Mylar
GIS Data sources
Same, plus DLGs DEMs Digital orthophotoquads
Data recorded as points, lines, areas using electronic devices
DLGs
Layer Feature Type
Public Land Survey System (PLSS) Township, range, and section lines
BoundariesState, county, city, and other national and
State lands such as forests and parks
TransportationRoads and trails, railroads, pipelines and
transmission lines
Hydrography Flowing water, standing water, and wetlands
DEMs
Digital elevation models
Usually 30 m resolution
Used to determine terrain attributes (slope aspect)
http://www.ngs.noaa.gov/RESEARCH/RSD/main/yakutat/yakori_full.html
DOQs Digital rep. of aerial
photographs Corrected for
image distortions Stored digitally
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Comparing traditional cartography & GIS: Storage & RetrievalTraditional Storage: points,
lines, areas drawn on map
Retrieval: Map reading
GIS Storage:
Points, lines, areas stored with spatial reference data (coordinates) & pointers
Tables of characteristics (attributes) associated with coordinates
Retrieval: Computer tracks where data are stored
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Comparing traditional cartography & GIS: Analysis & Output
Traditional Analysis: Limited to
data as presented on map
Output: Mapping
GIS Analysis: Allows
access to raw data can change aggregation or classification, or analyse further
Output: May include maps, tables, charts
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GIS Application Areas Government
Census Bureau: population Dept of Agriculture: soils data Dept of Defense/CIA: monitoring Dept of Transportation: roads data Political redistricting
Business Researching retail markets Evaluating site suitability Evaluating health care resources
Education & Research Land use change research Environmental monitoring Seismological research Population research
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Reasons for GIS applications Information Management
Data input Data editing Updating
Data output and display Maps Spatial information queries Time series of maps (tracking storms,
population growth, etc.)
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Reasons for GIS applications (Cont.)
Spatial Analysis Shortest Distance Buffer analysis Classification
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The Role of GIS within Geography GIS is an effective tool that integrates human
and physical geography GIS can combine (and overlay) human and
physical data Tool v.s. science
GIS is a tool for those who use it to conduct research on other subjects
GISci: Study of the fundamental issues arising from the creation, handling, storage, and use of geographic information
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To wrap up
What is geographic information? How do we get it? What do we do with it?
What is a GIS? Difference from CAC, CAD, analog
mapping GIS applications Tool versus science