polygonA = MULTIPOLYGON(((1701 985,3501 985,3501 2785,1701 2785,1701 985)))

polygonB = MULTIPOLYGON(((1698 1860,1698 1122,2598 1392,3492 1842,3492 32706,2598 2340,1698 1860)))

 

difference(polygonA, polygonB, polygonC)

-> polygonC == MULTIPOLYGON(((1701 1122,1701 985,3501 985,3501 2785,3492 1857,3492 1842,2598 1392,1701 1122)),((1701 1861,2598 2340,1669 2785,1701 2785,1701 1861)))

 

Both, polygonA and polygonB, satisfy is_valid(…), but polygonC doesn’t.

Is there anything wrong with the input? Is this a bug?

 

Regards

   Volker