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FAQ: What is the difference between generalized service area polygons and detailed service area polygons?

Question

What is the difference between generalized service area polygons and detailed service area polygons?

Answer

Generalized and detailed service area polygons are differentiated by the methods used to generate them, the amount of time it takes to generate them, as well as their relative overall accuracy of network coverage.

Generalized polygon generation
Generalized polygon generation is the fastest, yet least-accurate, method of service area polygon generation. Generalized polygon generation is achieved using only the geometries of the traversed junction source features. It does not incorporate the geometries of the traversed edge source features, as it assumes straight line edges for simplification, nor does it incorporate geometries of the non-traversed source features to generate exclusive coverage areas.

While it is the fastest method for generating service area polygons, this method can sometimes result in portions of edge features that are not actually a part of the service area being covered or partially covered by the generalized polygons. This may also sometimes result in portions of edge features that are a part of the service area being left outside of the generalized polygons. This especially occurs for very curvy source features near the periphery of the polygon and is due to the assumption of straight line edge features.
[O-Image] Example of generalized polygon generation
Detailed polygon generation
While detailed polygon generation is slower than generalized polygon generation, it is able to produce more accurate polygons in terms of appropriate network coverage. Detailed polygon generation is achieved by using the actual geometries of the traversed edge source features as well as incorporating the geometries of the non-traversed source features within the envelope of the network traversal area. This allows for more accurate network coverage by generating polygons which completely cover all traversed portions of the network and completely exclude all non-traversed portions of the network.
[O-Image] Example of detailed polygon generation