Build a topology
- Start up gvSIG OADE 2010. Load and display a polygon layer, e.g. aoi.shp in a Map View.
- Select Tools | Topology | Create Topology.
The Create topology wizard appears.
- Click Next.
- In the Topology name field, type in an appropriate name, e.g. SelfIntersection.
- In the Cluster tolerance field, type in a value, e.g. 1.
- In the Maximum number of errors field, type in a value, e.g. 20.
Note: this number is the maximum number of flag errors that can be generated. Errors exceeding the value will not be generated.
- Toggle on the polygon layer to include in topology, e.g. aoi.shp. Click Next.
The Topology rules page appears.
- Click Add.
The Topology rules dialog box appears.
- In the Topology rule drop down list, choose No polygon of A may contain a self-intersection. Click Ok.
- Click Finish.
In the legend, the polygon layer is now grouped under the SelfIntersection topology.
Validating the Topology
- In the legend, select the topology SelfIntersection to make it the active layer.
- Select Tools | Topology | Validate topology.
Processing messages appear and the validation results appear. A new error layer SelfIntersection_error is created and displayed in the SelfIntersection topology group and also in the map window.
Note: the SelfIntersection topology group icon has a red cross as shown above indicating the validation failed.
- Mouse right click on the SelfIntersection_error layer in the legend.
A pop up menu appears.
- Choose Attribute table.
The table: Attribute table:SelfIntersection_error appears.
- Scroll through the list of errors. Selecting one error record will highlight the corresponding error in the map window.