id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc 1198,ST_Union fails on some sets of polygons. Snapping works around the problem,dmiranda,pramsey," How to reproduce: -load either the attached shapefile or the sql into postgis -run the query: select st_union(geom) from st_union_topology_exception; -The following message should appear: ERROR: GEOSUnionCascaded: TopologyException: found non-noded intersection between LINESTRING (-54.7158 -28.0099, -54.7156 -28.0116) and LINESTRING (-54.7158 -28.0099, -54.7158 -28.0119) at -54.7158 -28.0099 SQL state: XX000 Other observations: -st_isvalid returns true for all the polygons -snapping may get rid of the problem (select st_union(st_snaptogrid(geom,0.00000000001)) from st_union_topology_exception; finishes without errors) -buffering by zero does not get rid of the problem -snapping stops solving the problem at 0.00000000000001, presumably near the float 64 resolution. possibly related to #575, #1045 and/or #1173 (error message is similar) Version: Ubuntu 11.04 Postgresql 9.1 postgis 2.0.0svn Rev: 7856 Last Changed Date: 2011-09-15 14:43:57 GEOS 3.4.0dev Rev: 3465 Last Changed Date: 2011-09-12 01:47:39 ",defect,closed,medium,PostGIS 2.0.0,postgis,master,wontfix,st_union topologyexception noded intersection,