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This Arcview extension provides a dialog-based tool to simplify the currently selected shapes in a polyline or polygon shapefile. This tool is used to generalize, or weed out, vertices that do not add to the desired level of detail in the geometry. A tolerance is specified to check whether or not vertices should be retained.
This script is a simple implementation of the Douglas – Peucker algorithm used in ARC/INFO and PC ARC/INFO. The dialog is initiated from a button in a View GUI.
- The extension does not make a new shapefile. It changes the currently active polyline or polygon shapefile. Changes can be Undone using the standard shape editing tools in Arcview.
- The extension will reduce the quality of the data. Any metadata for the themes should state that the data are modified.
- The extension will generalize all the selected polylines or polygons.
- Results are very dependent on the polyline or polygon geometry. While the shape endpoints are maintained, interior points may be eliminated. Other shapes in a network that may begin or end at an interior vertex may now be dangling. A complex shape may cross itself after being generalized. Neighboring polygons will no longer match edges. Proceed with caution.
- This script does not recalculate lengths or areas. They may have changed as the shapes are simplified. The View.CalculateFeatureGeometry (calcapl.ave) sample script can be used to update the values.