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Figure 5.76 Example of Vector Analysis and topology tools in GRASS.
Identifying duplicate polygons To identify duplicate polygons is effortless when importing the vectors into the GRASS plug-‐in. Let’s suppose, using the BREC output as an example, that the BREC building footprints have been extracted, converted to vector and then merged for the entire study area. There is the possibility that there will be an overlapping polygon at the seams. Thanks to the GRASS plug-‐in, when the vector layer is imported into GRASS. The plug-‐ in identifies and creates the duplicates, holes, islands, and whole vector as individual layers. Follow the instructions below to identify and remove duplicates. 1) Import vector into GRASS.