GTECH 361

1. GTECH 361 Lecture 10Behavior and the Geodatabase

2. Rules and Behavior • ..is what makes geodatabase features smart • Enforcing integrity with attribute domains • Grouping features using subtypes • Table relationships • Between feature classes • Between feature classes and non-spatial tables

3. Attribute Domains • Define what values are allowed for a field in a feature or a non-spatial table • Created and edited in ArcCatalog

4. Attribute Domains • Are a specialization of well-known data types • ValveTypeDomain is a Long Integer with a permissible value range from 1..10

5. Enforcing Data Integrity • Preventing errors during data entry • Checking validity after the fact

6. Types of Attribute Domains • Range domains • Coded value domains

7. Split and Merge Policies • Use attribute domains to specify how attributes are handled after the split or merge • Manage attributes that will be affected by edits to a feature's geometry

8. Split Policies • Duplicate • Default value • Geometry ratio

9. Merge Policies • Default value • Sum • Weighted average

10. Field Type Limitations to Split and Merge Policies

11. Subtypes • The closest we get to object-orientation in the geodatabase • To group similar features without creating a new feature class • Group parcels into residential, commercial, and agricultural subtypes and associate different attribute domains with each group • Faster than many feature classes

12. Subtypes in ArcGIS Versions • ArcView • Only displays subtypes • ArcEditor, ArcInfo • Create, edit and use subtypes

13. Example of a Subtype • Subtypes of feature class country_lanes

14. Example of a Subtype • Subtype encoding and decoding • Feature class table • ArcMap Table ofContents

15. Creating a Subtype • Based on an existing attribute, or • A new field containing subtype values • Values have to be short or long integer • For each subtype, you can associate default field values and domains • You have to define one default type • Once defined the new subtype can become target of an ArcMap edit operation

16. Using Subtypes with Features

17. Everything is Related… • to everything else but… (Tobler’s Law) • This multitude of relationships is usually not well captured in a GIS database • Which makes tracking real-world situations difficult • For instance…

18. Cardinality

19. Relationships Across Tables

20. Relationship Definitions • Require primary and foreign key to be of the same type • Supported field types are • short integer • long integer • float • double • text • object ID

21. Relationship Classes • Permanently stored in the geodatabase • Hence different from joins and relates in ArcMap, which are only stored in .mxd • Within but not across geodatabase(s) • Once created cannot be modified • If corresponding table is deleted, the relationship class is deleted automatically • Only 2 tables can be related per R.C.

22. Relationship Properties • Cardinality, origin and destination tables • As discussed before • Labels • Relationship types and messaging • Attributes

23. Relationship Labels • Relationship classes have forward and backward path labels

24. Relationship Types • SimpleTable objects exist independently of each other • CompositeDestination objects cannot exist without an origin object • Forward messaging only • One-to-one or one-to-many cardinality

25. Relationship Attributes • Relationship classes can have attributes describing the relationship • E.g, in a relationship between parcels and owners, an attribute of the relationship may be the percentage of ownership

26. Relationship Classes, Relates and Joins

27. Relationship Rules • Control how records in the origin and destination tables can be related • Which objects or subtypes from the origin table can be related to which objects or subtypes in the destination table • Specify a valid cardinality range for related objects or subtypes

28. Relationship Rule Example • Wood poles are able to support from 0 to 3 transformers, whereas steel poles support 0 to 5 transformers

29. In Summary • Modeling closer to real world by creating attribute domains, subtypes, and relationship classes • Attribute domains define the allowable values • Subtypes provide a way to implement different domains and relationships • Relationship classes create a permanent record of their relationship (as opposed to join/relate) • Relationship rules control which objects or subtypes from the origin table can be related to which objects or subtypes in the destination table

30. 3-Dimensional GIS TINs, DEMs and 3-D Surfaces

31. Surface Analysis in GIS • Analyzing the distribution of a variable which can be represented as the third dimension of spatial data • Elevation is a good example of a 3rd dimensional variable • Most GIS packages represent z-values as an attribute of the data

32. What is a DEM? • DEM = digital representation of a topographic surface (usually a raster or regular grid of spot heights) • DTM or digital terrain model = more generic term for any digital representation of a topographic surface, but not widely used • DEM is the simplest form of digital representation of topography and the most common • Resolution is a critical parameter

33. Creating DEMs • From contour lines (digital or scanned) • scanning, raster to vector conversion + additional elevation data are (i.e. shorelines provide additional contours) • algorithm is used to interpolate elevations at every grid point from the contour data

34. Creating DEMs • By photogrammetry (manually or automatically) • extraction of elevation from photographs is confused when the ground surface is obscured e.g. buildings, trees • DEMs from each source display characteristic error artefacts

35. Background of TINs • Developed in the early 1970's as a simple way to build a surface from a set of irregularly spaced points ….. .....Commercial systems using TIN began to appear in the 1980's as contouring packages, some embedded in GISs

36. Surface Analysis in a Vector GIS • Several ways of building a TIN are possible: • from a set of irregularly-spaced points • from points in a regular fashion - a lattice • from digitized contours as line features • Not usually practical to use polygon features

37. The TIN Model • Sample points are connected by lines to form triangles • Each triangle's surface would be defined by the elevations of the three corner points • Pros and cons of TINs

38. TIN Construction

39. From Points to Surfaces

40. Exaggerating Elevations

41. Terrain Analysis in Concert With Other GIS Operations

42. Calculating Slope and Aspect • From (raster) DEMs: • to estimate these at a raster point, a 3x3 window centered on the point is usually used • From TINs: simpler and more efficient, but perhaps not as accurate

43. What Is Slope?

44. Slope and Aspect Calculation

45. Determining Drainage Networks • A raster DEM contains sufficient information to determine general patterns of drainage and watersheds • Flow direction determined by the elevations of surrounding cells • Algorithms to determine the flow direction • Water is assumed to flow from each cell to the lowest of its neighbors

46. Flow Direction DEM

47. Leading to Flow Accumulation

48. Three Steps in Developing a Hydrological Model Flow Directions Accumulating Flow Critical Flow Level 2

49. Very Important Points

50. Relief Shading