[geos-devel] Issues with relate not handling GeometryCollections?

Martin Davis mbdavis at VividSolutions.com
Thu Dec 5 12:38:26 EST 2002

 Here's an example show why a robust approach is require to the issue of relating GeometryCollections.  In the attach image, you have to be able to tell whether the red line intersects the exterior of the two blue triangles.  This could require more precision than supplied by double precision numbers.

Currently the only way I can think of doing this robustly is to compute the arrangement of the intersections exactly, and then examine the resulting line segments for their location to one another.  It's basically the same problem as for computing overlays robustly, but at least in this case you can report the results precisely,  since the output is just a boolean.
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