Hi, Just a quick one, you could try the Topology Checker https://docs.qgis.org/2.8/en/docs/user_manual/plugins/plugins_topology_checker.html
This should help you locate things like Self Intersections. You will have to manually fix the error, but at least you have a way to find the issues. Regard’s, Richard. —— Richard McDonnell MSc GIS, FME Certified Professional FRM Data Management —— Oifig na nOibreacha Poiblí Office of Public Works Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36 Jonathan Swift Street, Trim, Co Meath, C15 NX36 —— M +353 87 688 5964 T +353 46 942 2409 https://gov.ie/opw —— To send me files larger than 30MB, please use the link below https://filetransfer.opw.ie/filedrop/[email protected] Email Disclaimer: https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/ —— MSc GIS, FME Certified Professional —— Oifig na nOibreacha Poiblí Office of Public Works Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36 Jonathan Swift Street, Trim, Co Meath, C15 NX36 —— M +353 87 688 5964 T +353 46 942 2409 https://www.opw.ie —— Email Disclaimer: https://www.opw.ie/en/disclaimer/ From: Qgis-user <[email protected]> On Behalf Of Alister Hood Sent: 01 June 2021 23:06 To: [email protected] Subject: Re: [Qgis-user] Is this a bug in the vector clipping algorithm? 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 <[email protected]<mailto:[email protected]>> To: [email protected]<mailto:[email protected]> Subject: Re: [Qgis-user] Is this a bug in the vector clipping algorithm? Message-ID: <[email protected]<mailto:[email protected]>> 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 Please note that the existing 01-6476XXX / 046-9426XXX numbering ranges will no longer be available after 30th April 2021.
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