[GIS] polygon map overlay algorithm

algorithmgeometryoverlayvector

There are many algorithms for binary map overlay operation in vector data format which take two layers of map and produce resultant layer i.e overlaid layer as output.
I am wondering whether there are any algorithms which take more than two layers say 3 layers simultaneously and produce the overlay result?

Best Answer

The low-level spatial predicate operators are all binary—i.e., compare geometry A to geometry B. For example, see the DE-9IM topological model, which is the basis for Intersects, Contains, etc. When you have more than two, say geometry C, then you might need to compare the combinations of geometries: AB, AC, BC. But it all really depends on what you are trying to determine.

For a specific coded example of how you handle more than two geometries, see Polygon overlay with Shapely. This example also features a cascaded union, which unions several (more than two) geometries, so I guess is a good example of an efficient map algorithm that take takes more than two inputs.

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