Topological Errors: Topological Relationships and Errors in Geometric Features and between Layers (Especially for GATE-Geospatial 2022)

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Topological errors violate the topological relationships that are either required by a GIS package or defined by the user.

Topological Relationships

The coverage has three topological relationships:

  • Connectivity
  • Area definition
  • Contiguity
This Diagram Shows Three Topological Relationships

If digitized features did not follow these relationships, they would have topological errors. The geodatabase data model from ESRI, Inc. has a total of 25 topology rules that apply to point, line, and polygon features.

Using the geodatabase data model, we can choose the topological relationships to implement in the data sets and define the kinds of topological errors that are important to a project.

This Image Shows Two Topological Errors That Are Important T …

Topological Errors with Geometric Features

The topological relationships incorporated into the coverage model apply to the geometries of simple features in a single layer.

  • Topological errors with polygon features include unclosed polygons, gaps between polygons and overlapping polygons.
  • Point features have few topological errors. The coverage model requires a label point to link a polygon to its attribute data.
Illustration 2 for Topological_Errors_with_Geometr …

Topological Errors between Layers

The coverage model allows the user to work with topological errors in a single coverage. But the new database data model, we can find and fix topological errors of spatial features between two or more layers.

A common error between two polygon layers is that their outline boundaries are not coincident. One type of error with two-line layers occurs when line features from one layer do not connect with those from another layer at end points.

This Figure Shows Topological Errors between Layers

In above figure, Line features from one layer do not connect perfectly with those from another layer at end points. (b) is an enlargement of the top error in (a) .

For example, when we merge two highway layers from two adjacent states, we expect highways to connect perfectly across the state border. Errors can happen if highways intersect, or overlap, or have gaps. Other errors with line layers include overlapping line features and line features not covered by another set of line features.

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