When attempting to union multiple polygons with Shapely 1.5.6 in Python 2.7.9, using GEOS 3.4.2, I get the following error in the underlying C++ code:
Assertion failed: (!"should never be reached"), function itemsTree, file AbstractSTRtree.cpp, line 371
The polygons are in a Python list and then I call
shapely.ops.unary_union(polygon_list). The polygon list has 1998 items, all of which are proper polygons. I have tried running the
unary_union operation in a separate python session with a couple manually created polygons and it works.
Could the number of polygons be a problem, or the import order in the file (I have seen a mention of shapely needing to be imported before Basemap, but I am not using that package)?