1. ArcGIS Topology Shapefiles, Coverages, Geodatabases
Friday 03/03/06
GEOG 4103

2. Topology in GIS
generally defined as the spatial relationships between adjacent or neighboring features
implemented through data structure

3. Components
Connectivity: Arcs are connected to others (at nodes). This identifies possible routes and networks, such as rivers and roads..
Containment: An enclosed polygon has a measurable area; lists of arcs define boundaries and closed areas.
Contiguity: The adjacency of polygons can be determined by shared arcs.

4. Polygon A has arcs a1,a2, a3
Node 1 is connected with arcs a2, a1, a6
arc a5 has polygons C (right) and B (left)

5. Data Structures COVERAGE Files are stored in two directories
Coverage name – unique files for the coverage
INFO – files for all the coverages in that workspace/directory
Exchanged using ARC/INFO Exchange Files (.E00)

6. Coverages Coverages can be point, line or polygon
A single coverage can have points and lines, or lines and polygons, but never points and polygons
Polygon coverages partition the area into polygons
No overlap allowed between polygons
All areas in the coverage are part of some polygon

7. Coverages Coverages are created using the BUILD and CLEAN commands
CLEAN attempts to fix problems in topology, sometimes moving points and lines
BUILD assumes the topology is “clean” and fails if topological problems are encountered
It creates Point, Arc and Polygon attribute tables (PAT, AAT)

8. Arc Attribute Table (AAT)
arcs have attributes which identify the polygons on either side
"left" and "right" by reference to the sequence in which the arc is coded
topological relationships stored in AAT
I.e. adjacent polygon IDs in the LPoly and RPoly fields.

9. Grids Deal with RASTER (gridded) data
Each grid cell contains a single number
Files are stored in several directories, so to move a grid it is safest to EXPORT it
Grids have a .VAT or Value Attribute Table that relate codes in the grid to associated attributes

10. Shapefiles Shapefiles
Comprised of 4 files – coverage.shp, .sbn, .sbx and .dbf
The .dbf file contains the attribute data and can be opened with Excel, Access and other database editors that understand the .dbf format

11. Shapefiles
Polygons in shapefiles CAN overlap, while in a COVERAGE they CANNOT
so: to convert SHAPEFILES to COVERAGES
Overlaps need to be eliminated

12. Geodatabases
“Geodatabase = An object-oriented geographic database that provides services for managing geographic data. E.g relationships, and topological associations.
contains feature datasets and is hosted inside of a relational database management system.”

13. Geodatabases Geodatabases are stored in relational databases
Many large GIS users have large Oracle-based database systems that are used for GIS data using the ESRI Spatial Database Engine for conversion
You can also have “Personal Geodatabases” that are maintained on the local machine

14. ArcGIS Components ArcCatalog ArcMap ArcToolbox ArcScene Manage data
Create maps
Analysis
ArcToolbox
Stand-alone Analysis and Conversion
ArcScene
3-D display

15. ArcCatalog

16. ARCGIS Components
ARC Catalog

17. ArcCatalog Locate Data for use with ARCGIS What data is available?
Local Disks
Databases
Internet/Online
What are the properties of that data?

18. ArcCatalog - Preview
Preview Geodata and Tables

19. Metadata
ArcCatalog will also display or allow editing of simplified Metadata

20. ArcMap

21. ARGIS Components
ARCMAP

22. ArcMap advantages better map quality Projections
Automatically reprojects data to match the map projection (now you can mix and match UTM and Lat-Lon coverages)
But only if the source projection is defined
Transparency: can see through one layer

24. ArcMap Toolbars Movable toolbars
You select the toolbars you want from the View menu

25. Toolbars can be moved or put in separate windows

26. Tips
Adding more buttons (customizing ArcMap)
Continuous pan/zoom

27. ArcToolbox

28. ArcToolbox
The ArcToolbox component of ArcGIS contains sets of stand-alone wizards designed to help you perform specific tasks

29. ArcScene

30. ArcScene – 3 D Data Viewer
ArcScene is a 3-D data viewer that allows you to get different perspectives on three-dimensional landscapes
Tilt and rotate
View from a point

32. ArcReader
Free!

33. ArcReader
ArcReader is a FREE stand-alone tool designed for DISPLAY and printing of local and web-accessible geodata
It requires that the map to be displayed be “published” to a special PMF file using an ARCGIS extension