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Designing a geodatabase topology

Designing a geodatabase topology

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Here is the process used to develop a topology design before you use ArcGIS to create a topology in the geodatabase.

  1. Make a list of the desired feature classes that will share geometry.
  2. Specify the spatial representations of each feature class (e.g., point, line, or polygon).
  3. List the feature classes that will share geometry and will be edited and maintained together. For example, if you perform an edit on the geometry of one of the features, the others will be updated as well.

  4. Some feature classes commonly managed in a shared topology
    Data theme Feature classes Subsample of topology rules
    Parcels Parcel polygons

    Parcel boundaries (lines)

    Parcel corners (points)
    Parcel polygons must not overlap.

    Parcel polygon boundaries must be covered by parcel boundary lines.

    Parcel boundary endpoints must be covered by parcel corner points.
    Street centerlines and census units Street centerlines

    Census blocks

    Census block groups

    Census tracts
    Street lines must not intersect or touch interior.

    Census blocks must not overlap.

    Census block groups must be covered by census blocks.

    Census block groups must not overlap.

    Census tracts must be covered by census block groups.

    Census tracts must not overlap.
    Soils Soil type polygons Soil polygons must not overlap.

    Soil polygons must not have gaps.

    Hydrology Hydro lines

    Hydro points

    Watersheds (polygons)
    Hydro lines must not self-overlap.

    Hydro points must be covered by hydro lines.

    Watersheds must not overlap.

    Watersheds must not have gaps.

  5. Organize these feature classes into a feature dataset.
  6. Specify topology rules between the elements in each individual feature class. For example, parcels can be single-part or multipart polygons. Adjacent parcels share geometry. Parcels cannot overlap.
  7. Specify the topology rules between feature classes. For example, the lines that define parcel polygons must be covered by parcel boundary lines.
  8. Identify the accuracy ranks of the coordinates in each feature class. The most accurate feature classes should receive a rank of 1 and lower accuracies descend in order from the highest rank (the second most accurate gets a rank of 2 and so on). Multiple feature classes can have the same accuracy rank. If you cannot perceive that there is a difference in accuracy, set the ranks of all features classes to 1 (i.e., their accuracy is the same). See the "Cluster processing" section Topology in ArcGIS for information on how coordinate ranks are used during topology validation and processing.
  9. Build a test geodatabase (using a file or a personal geodatabase) with a copy of your features to test your proposed topology design. Exercise your prototype geodatabase. For example, add a topology based on your proposed design, validate it, and edit some of the features. This will give you insight into behavior and help you refine your design.
  10. Refine and adjust your design until you have a working implementation.

A good book from ESRI Press named Designing Geodatabases: Case Studies in GIS Data Modeling by David Arctur and Michael Zeiler provides good examples. Also see