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Previous: Projection Definition and Coordinate Transformation
In this exercise, you will learn how to perform a union between overlapping polygon features using theAreaOnAreaOverlayer. The AreaOnAreaOverlayer is typically used for three main operations: (1) deconstruct overlapping polygons to produce the intersections and differences, (2) compare multiple datasets for area overlaps, and (3) area calculations based on overlapping area data.
polygon-in-polygon-overlay.fmwt
Note: Since you areworking on a public facing database, tables can occasionally be overwritten and/or modified. If your translation produces unexpected results, see theResetting the PostGIS Training Databasearticle.或者,您可以下载提供的文件(s) and replace the PostGIS reader with a reader of the appropriate format.
In this scenario, you will be performing area calculations based on overlapping historic zones and neighborhood polygons. This will allow you to identify which historic areas belong to each neighborhood and the total area of each historic zone.
The AreaOnAreaOverlayer transformer will perform an area-on-area overlay for intersecting polygons - all polygons are considered against each other, and where they overlap, new polygons are created that represent both the overlapping area and the original areas with the overlap removed. For more technical details about the AreaOnAreaOverlayer. For more technical details about the AreaOnAreaOverlayer, see theDocumentation.
Note: area is calculated in square map units. For a more in-depth tutorial on area calculations, see theArea Measurements with the AreaCalculatorarticle.
Data used in this tutorial originates from open data made available by theCity of Vancouver, British Columbia. It contains information licensed under the Open Government License - Vancouver.
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