Hi list, As there were doubts expressed on this list regarding performance in more challenging environments, an additional test is provided. The resulting figures of GGL are still good, sometimes the best, sometimes the second best. For example, for a union on polygons with many diagonals, holes, and many points on both inputs: ggl 3.6 seconds b.p. 7.8 seconds terralib 8.2 seconds geos 35.9 seconds cgal 77.8 seconds (a cgal-intersection (instead of union) is the fastest in these tests) Polygons have large diagonals, holes are tested, and the number of vertices of both input polygons can be varied in the tests. More information: http://trac.osgeo.org/ggl/wiki/IntersectionStarComb, including references to sources for reproducing the figures, everyone is invited to do that. Regards, Barend