Hello All, > SELECT geomunion(SnapToGrid(geomset.geom,0.00001)) ... I had a similar problem using intersection() and SnapToGrid() also solved it. I think it would be good if this could be mentioned in the PostGIS manual. > > > >>NOTICE: TopologyException: no outgoing dirEdge found (-3.85329,44.7512) > > > >> > > > >>ERROR: GEOS union() threw an error! Regards, Steffen