Hi, The error message reports that one of your input geometries was invalid, meaning that it is self-intersecting or otherwise "invalid" to the GEOS algorithms. I'm pretty sure that GEOS (and Shapely) will not return an invalid geometry, and if it did it would be a bug.
Sean On Aug 30, 2009, at 3:20 AM, zhongshq wrote: > > I use MultiPolygon to execute polygons boolean operation in Python > by Shapely > 1.0.12. > > multipolygon1 = MultiPolygon(....) > multipolygon2 = MultiPolygon(....) > > multipolygon3 = multipolygon1.intersection(multipolygon2) > > python return the following information: > > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > File > "/export/eda/edatools/linux/tools/lib/python2.6/site-packages/ > Shapely-1.0.12-py2.6.egg/shapely/topology.py", > line 24, in __call__ > "The operation '%s' produced a null geometry. Likely cause is > invalidity > of the geometry %s" % (self.fn.__name__, repr(context)) > shapely.geos.TopologicalError: The operation 'GEOSIntersection' > produced a > null geometry. Likely cause is invalidity of the geometry > <shapely.geometry.multipolygon.MultiPolygon object at 0x10d6c050> > > I guess in the operation (intersection), it generated invalid > polygon, so it > can't finish the operation. But before executing the operation, how > can I > know it will generate illegal polygon? > > Thanks > > -- > View this message in context: > http://www.nabble.com/issue-of-MultiPolygon-operation-in-Shapely-1.0.12-tp25167247p25167247.html > Sent from the PrimaGIS mailing list archive at Nabble.com. > > _______________________________________________ > Community mailing list > [email protected] > http://lists.gispython.org/mailman/listinfo/community -- Sean _______________________________________________ Community mailing list [email protected] http://lists.gispython.org/mailman/listinfo/community
