1. Copyright © 2006 by Maribeth H. Price 13-1 Chapter 13 Working with Geodatabases

2. Copyright © 2006 by Maribeth H. Price 13-2 Outline Understanding the geodatabase model Creating a geodatabase Importing layers into a geodatabase Setting up a feature dataset and importing layers Setting up and using attribute domains Using split and merge policies

3. Copyright © 2006 by Maribeth H. Price 13-3 Geodatabases Feature datasets Feature classes

4. Copyright © 2006 by Maribeth H. Price 13-4 Create geodatabase In ArcCatalog

5. Copyright © 2006 by Maribeth H. Price 13-5 Feature datasets Related feature classes Common coordinate system May participate in topologic relationships and networks

6. Copyright © 2006 by Maribeth H. Price 13-6 Key concepts for feature classes Establishing the spatial reference –Reviewing the domain and resolution –Version 9.2 geodatabases Setting tolerances Creating feature datasets and feature classes Importing feature classes to feature datasets or geodatabases

7. Copyright © 2006 by Maribeth H. Price 13-7 Review: The Spatial Reference Every data set requires a complete description of its coordinate system for proper display and analysis –Geographic coordinate system / datum –Projection (if one is used) –Storage units used to store the x-y values (degrees, feet, etc.) –Domain, or maximum allowable x-y values –Resolution, or the x-y precision

8. Copyright © 2006 by Maribeth H. Price 13-8 Domain and Resolution Domain –Maximum allowable x-y values –If a feature’s values exceed the domain, the feature won’t be stored in the feature class Resolution –The precision to which x-y values are stored Same units as the storage units Resolution of 0.001 indicates values are stored to nearest thousandth of the storage units

9. Copyright © 2006 by Maribeth H. Price 13-9 Domains for unprojected data Unprojected data are stored in degrees –Require a small domain (0-180) but a high resolution * At the equator 1 deg = 110 km* 0.001 deg = 110 m 0.000001 deg = 0.1 meters

10. Copyright © 2006 by Maribeth H. Price 13-10 Domains for projected data National or world maps need a large domain but less resolution. Local maps need a small domain and more resolution. 8 million meters1000 meters

11. Copyright © 2006 by Maribeth H. Price 13-11 Setting the domain/resolution When creating a feature dataset, ArcGIS chooses a default domain and resolution based on the coordinate system you choose. Advanced users may choose to customize these values when needed.

12. Copyright © 2006 by Maribeth H. Price 13-12 Domains vs Extents The domain is the maximum allowable range of values that can be stored The extent of a spatial data set indicates the range of x-y values actually present in the data Stored map units

13. Copyright © 2006 by Maribeth H. Price 13-13 9.2 Geodatabases Previous versions used only 4-byte integers to store x-y coordinates. –Required tradeoffs between domain and resolution (precision) –Users had to pay close attention to setting the domain and precision appropriately Version 9.2 geodatabases use 10-byte integers –Tradeoff no longer an issue –ArcGIS chooses default domain and precision based on the specified coordinate system –Specialized applications may need to change defaults

14. Copyright © 2006 by Maribeth H. Price 13-14 Implications It’s a LOT easier to set up a feature dataset BUT Version 9.1 and previous geodatabases must be upgraded to Version 9.2 –9.1 gdb’s can be used with V9.2 but not all functions will work properly –9.2 gdb’s cannot be used with V9.1 software Organizations need to plan their upgrade to V 9.2 carefully.

15. Copyright © 2006 by Maribeth H. Price 13-15 Tolerances During geometry operations (like buffering, intersect, editing, etc) tolerances are used to determine whether two features should be the same. The tolerance is the maximum distance a feature vertex can be moved to coincide with another vertex. Tolerance a c b a c b gap overlap Coincident lines? Clustering

16. Copyright © 2006 by Maribeth H. Price 13-16 Types of tolerance XY Tolerance is set for a feature class –Previously called the cluster tolerance –Used during geoprocessing operations such as clip, buffer, intersect, etc. –Avoids tiny slivers and dangles –Can override it using geoprocessing environment settings if needed Cluster tolerance now refers to topology operations. –Can override default XY tolerance when setting the cluster tolerance for a topology. Cluster tolerance must be larger than the XY tolerance, however.

17. Copyright © 2006 by Maribeth H. Price 13-17 Default tolerance Set based on coordinate system units and is equivalent of 1mm –0.001 meter –0.003281 feet (0.03937 inches) –0.0000000556 degrees Give good results in most scenarios The XY tolerance always be smaller than your data capture resolution

18. Copyright © 2006 by Maribeth H. Price 13-18 Creating feature datasets

19. Copyright © 2006 by Maribeth H. Price 13-19 Importing feature classes Single or batch tools Use SQL to select only certain features Layer CS will be automatically projected if different from the feature dataset CS

20. Copyright © 2006 by Maribeth H. Price 13-20 New feature class

21. Copyright © 2006 by Maribeth H. Price 13-21 Using geodatabase features Default values for attributes Domains Split and merge policies Subtypes

22. Copyright © 2006 by Maribeth H. Price 13-22 Using default attributes Automatically assign default values as features are added.

23. Copyright © 2006 by Maribeth H. Price 13-23 Domains Rules for data entry –Prevent typing errors –Can verify that values fall into correct range Created for entire database Can be re-used in different feature classes

24. Copyright © 2006 by Maribeth H. Price 13-24 Domain types Range domain: Percentage Coded domain: PipeSize

25. Copyright © 2006 by Maribeth H. Price 13-25 Domain examples

26. Copyright © 2006 by Maribeth H. Price 13-26 Domain uses Save space by storing numeric code, but set up domain for easy interpretation of values

27. Copyright © 2006 by Maribeth H. Price 13-27 For coded domains For range domains Creating domains

28. Copyright © 2006 by Maribeth H. Price 13-28 Merge Policies Rules for assigning attributes when features are merged Saves attribute update time

29. Copyright © 2006 by Maribeth H. Price 13-29

30. Copyright © 2006 by Maribeth H. Price 13-30 Split Policy

31. Copyright © 2006 by Maribeth H. Price 13-31 Subtypes Integer-coded classes of features Automatic display with different symbols Each subtype can have own default values ArcView can view subtypes, editing requires ArcEditor or ArcInfo