On Mon, 7 May 2012 18:57:17 +0200, Sandro Santilli wrote:
How did you import the geometries ?
Serendipity, i.e. finding something useful by pure hazard :-) Short report explaining this puzzling mystery: - the disputed Geometry has *two* distinct rings - the main one is correctly marked in the SHP as the exterior ring [about 200 vertices] - the second one has only 4 vertices (i.e. it's a triangle) and is almost invisible, because is incredibly small (just few centimeters, measured on the terrain: it looks like a possible artifact). this second ring is correctly marked in the SHP to be an interior ring, and shares a common point with the exterior ring. nothing forbids an interior ring like this, so GEOS correctly identifies this Polygon as a valid one. There was a bug in the SpatiaLite's own SHP loader: on SpatiaLite the second ring was wrongly assumed to be a second exterior ring, thus producing a MultiPolygon (two polygons). But the second polygon was fully contained within the main one, thus causing GEOS to raise a geometry error. Conclusion #1: we've found (and resolved) an obscure bug in SpatiaLite Conclusion #2: GEOS surely is the better tool to be used in order to identify any malformed Geometry Highly recommended ;-) bye Sandro p.s.: many thanks to Pasquale, Salvatore and Strk -- Il messaggio e' stato analizzato alla ricerca di virus o contenuti pericolosi da MailScanner, ed e' risultato non infetto. _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
