1. Lecture Materials by Austin Troy except where noted© 2008 Part 3. Regions Topology and advanced vector queries ------Using GIS-- Fundamentals of GIS

2. Lecture Materials by Austin Troy except where noted© 2008 Regions Topology Allows for Nested representation: allows for hierarchical nesting of certain polygon types within larger polygon types Example: a regions layer may contain block groups within tracts within counties, within states, each level with their own behaviors and each with their own membership; The former Soviet Union through time

3. Lecture Materials by Austin Troy except where noted© 2008 Regions Topology Allows for Associations: dispersed or connected polygons can be given membership in the same feature; deals with “void area” Example: Hawaii or Florida; each comprised of many sub- features, but computer recognizes them as single entity

4. Lecture Materials by Austin Troy except where noted© 2008 Regions Topology Allows for Overlapping geographic features: features that are not spatially mutually exclusive, but overlap can be coded for Example: fire perimeters, overlapping soils or geologic data at different layers From ESRI ‘s ArcINFO help

5. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1880-1900

6. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1900-1915

7. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1915-1930

8. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1930-1945

9. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1945-1960

10. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1960-1975

11. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1975-1990

12. Lecture Materials by Austin Troy except where noted© 2008 Fire perimeters over time 1990-2001

13. Lecture Materials by Austin Troy except where noted© 2008 Regions and Subclasses In Arc/Info a grouping of polygons that share some logical grouping are called a subclass Each hierarchical level is a subclass in this case From ESRI ‘s ArcINFO help

14. Lecture Materials by Austin Troy except where noted© 2008 Regions and Subclasses This allows attribute data to be stored much more efficiently. attributes can be associated with them which are distinct from the attributes associated with the individual polygons Region attributes are stored in subclass-level attribute tables that are named cover.PATregionsubclass (e.g. Census.PATcounty).

15. Lecture Materials by Austin Troy except where noted© 2008 Regions and Subclasses In the upper one, the three islands are managed as a subclass In the lower, 103, 104 and 105 refer to areas of fire damage for three given years, each managed as a subclass From ESRI ‘s ArcINFO help

16. Lecture Materials by Austin Troy except where noted© 2008 Methods for Making Regions AREAQUERYa dynamic polygon overlay tool that allows you to integrate, query, and aggregate polygon and region layers from multiple coverages in a single operation. POLYREGIONconverts a polygon coverage to a region subclass. All polygons in the in_cover become a region of the output subclass. REGIONBUFFER creates buffer regions around specified input coverage features. REGIONCLASScreates preliminary regions from arcs by region subclass, or appends preliminary regions to existing regions for the subclass. REGIONCLEAN merges adjacent polygons that belong to the same regions. REGIONDISSOLVE constructs new region subclasses by aggregating polygons or regions with the same value for a specified item. REGIONJOIN creates new regions by joining a related table to a region subclass attribute table. REGIONQUERY creates new regions from existing regions or polygons based on attribute values in multiple subclasses and specified output items. REGIONXTAB an ATOOL enabling you to do region cross tabulation. In ARCEDIT MAKEREGIONcreates regions from selected polygons. From ESRI ‘s ArcINFO help

17. Lecture Materials by Austin Troy except where noted© 2008 Example: Areaquery This is an extremely helpful tool for doing multi-layer queries with a minimum of steps Utilizes the regions approach for analysis, querying and manipulation of overlapping coverages Areaquery’s power lies in its ability to integrate many coverages (up to 32) into one “super-coverage” so all the coverages can be analyzed Can do queries for highly specific criteria, and on numerous attributes Similar to doing multiple unions, but simpler and more data efficient

18. Lecture Materials by Austin Troy except where noted© 2008 Areaquery Say you want to do a specific query for the following: – landtype is brushland, soil is suitable for development, site within 300 meters of sewer line, site is 20 meters beyond existing streams and the site must contain a contiguous area of 8000 square meters First, you specify each coverage to be analyzed; in the process, each polygon coverage is turned into a regions cover Then you specify a logical query across data sets

19. Lecture Materials by Austin Troy except where noted© 2008 Areaquery example Say we’re doing a site selection where: preferred landuse is brushland Soil types should be suitable for development Site must be within 300 meters of existing sewer lines Site must be beyond 20 meters of existing streams Site must contain an area of at least 8000 meters square These codes are specific to the coverages in our database: – LANDUSE (attribute LU-CODE = 300 - brushland) – SOILS (attribute SUIT >= 2 - suitable for development), – SEWERBUF (a 300 meter buffer around sewerlines) – STREAMBUF (a 20 meter buffer around streams). From ESRI ‘s ArcINFO help

20. Lecture Materials by Austin Troy except where noted© 2008 Areaquery From ESRI ‘s ArcINFO help

21. Lecture Materials by Austin Troy except where noted© 2008 Areaquery example Now let’s say we wanted to try this on our habitat site selection example we did in lab We would start by turning all our buffer feature classes into coverages in Arc Catalog

22. Lecture Materials by Austin Troy except where noted© 2008 Areaquery example Then input expression Followed by the coverage names and subclass names

23. Lecture Materials by Austin Troy except where noted© 2008 Areaquery example Followed by your logical expression, which here is just presence/absense

24. Lecture Materials by Austin Troy except where noted© 2008 Areaquery results You get a coverage with a bunch of subclass, one for your desired conditions, and one for each constituent subclass Hence, this becomes like an Arc/Info version of a geodatabase

25. Lecture Materials by Austin Troy except where noted© 2008 Areaquery results Here’s land meeting all our criteria

26. Lecture Materials by Austin Troy except where noted© 2008 One more example Now let’s say we’re looking for vacant land (LUcode=3100) that is in a floodplain (not $FLOOD) and not on public land (not $open), so that the government can target areas to buy to prevent future floodplain development

27. Lecture Materials by Austin Troy except where noted© 2008 Areaquery example 2 Again we specify our function and then our subclasses Then our criteria

28. Lecture Materials by Austin Troy except where noted© 2008 Areaquery example 2 Then we get the following result