OK, I thought I had tried "Check validity" with both QGIS and GEOS methods, but I must have got confused and only used GEOS method, which doesn't detect an error. The first tool I tried was actually "Fix geometries", which also thinks the geometries are valid. Maybe fix geometries uses GEOS and needs to be enhanced with a QGIS method. It seems strange for other algorithms like "clip" to do more fixing than "fix geometries", especially in a case like this where you would think the feature could be clipped without any "fixing".
Thanks. Date: Tue, 1 Jun 2021 02:45:51 -0700 (MST) > From: Andrea Giudiceandrea <andreaer...@libero.it> > To: qgis-user@lists.osgeo.org > Subject: Re: [Qgis-user] Is this a bug in the vector clipping > algorithm? > Message-ID: <1622540751842-0.p...@n6.nabble.com> > Content-Type: text/plain; charset=us-ascii > > Alister Hood-2 wrote > > I haven't been able to find a tool for validating or repairing geometries > > that thinks there is a problem with the original geometry > > Hi Alister, > what tool have you used to check the geometry? > > Have you tried to use the Geometry Checker core plugin (Vectror->Check > Geometries) or the "Check validity" (qgis:checkvalidity) processing tool > (with the QGIS method)? > They both report errors: "duplicate node", "self contact", "duplicate > nodes". > > Also the ArcMap/ArcGIS Check Geometry tool reports "self intersections". > > Anyway it seem the QGIS Clip tool does a "sanitize" of the intersection > result (always converting to Multi Type). > > Regards. > > Andrea Giudiceandrea >
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