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Analysis and Modeling in GIS
12/07/10 Ron Briggs, UTDallas GISC 6381 GIS Fundamentals 1
GIS and the Levels of Science
Description:
Using GIS to create descriptive models of the world --representations of reality as it exists.
Analysis:
Using GIS to answer a question or test an hypothesis.
Often involves creating a new conceptual output layer, (or table or chart), the values of which are some transformation of the values in the descriptive input layer.
--e.g. buffer or slope or aspect layers
Prediction:
Using GIS capabilities to create a predictive model of a real world process, that is, a model capable of reproducing processes and/or making predictions or projections as to how the world might appear.
--e.g. flood models, fire spread models, urban growth models
12/07/10 Ron Briggs, UTDallas GISC 6381 GIS Fundamentals 2
The Analysis Challenge
• Recognizing which generic GIS analytic capability (or combination) can be used to solve your problem:
– meet an operational need
– answer a question posed by your boss or your board – address a scientific issue and/or test a hypothesis
Send mailings to property owners potentially affected by a proposed change in zoning
Determine if a crime occurred within a school’s “drug free zone”
Determine the acreage of agricultural, residential, commercial and industrial land which will be lost by construction of new highway corridor
Determine the proportion of a region covered by igneous extrusions
Do Magnitude 4 or greater sub-oceanic earthquakes occur closer to the Pacific coast of South America than of North America?
Are gas stations or fast food joints closer to freeways?
12/07/10 Ron Briggs, UTDallas GISC 6381 GIS Fundamentals 3
Availability of Capabilities in GIS Software
• Descriptive Focus: Basic Desktop GIS packages – Data editing, description and basic analysis
– ArcView – Mapinfo
– Geomedia
• Analytic Focus: Advanced Professional GIS systems
– More sophisticated data editing plus more advanced analysis
– ARC/INFO, MapInfo Pro, etc.
Provided through extra cost Extensions
or professional versions of desktop packages
• Prediction: Specialized modeling and simulation – via scripting/programming within GIS
» VB and ArcObjects in ArcGIS » Avenue scripts in ArcView 3.2
» AMLs in Workstation ARC/INFO (v. 7)
Write your own or download from ESRI Web site – via specialized packages and/or GISs
» 3-D Scientific Visualization packages
Capabilities move ‘down the chain’ over time.
In earlier generation GIS systems, use of advanced applications often required learning another package with a different user interface and operating system (usually UNIX).
» transportation planning packages e.g TransCAD » ERDAS, ER Mapper or similar package for raster
Description and Basic Analysis (Table of Contents)
• Spatial Operations Vector
– spatial measurement
– Centrographic statistics – buffer analysis
– spatial aggregation » redistricting
» regionalization » classification
– Spatial overlays and joins
Raster
– neighborhood analysis/spatial filtering
• Attribute Operations – record selection
» tabular via SQL
» ‘information clicking’ with cursor
– variable recoding – record aggregation
– general statistical analysis
– table relates and joins
– Raster modeling
12/07/10 Ron Briggs, UTDallas GISC 6381 GIS Fundamentals 5
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