You can run the 'Check Validity' tool from the Processing Toolbox with 'QGIS' method and it will point out the error. (see screenshot <https://imgur.com/a/yIP947p>) 'line 1 contains 3 duplicate nodes starting at vertex 13'. So QGIS will try to fix this by creating a multipart geometry. [image: Logo] <https://spatialthoughts.com/> Ujaval Gandhi Spatial Thoughts mobile: +91-8095684687 email: [email protected] [image: LinkedIn icon] <https://www.linkedin.com/in/spatialthoughts/> [image: Twitter icon] <https://twitter.com/spatialthoughts>
On Tue, Jun 1, 2021 at 1:59 PM Alister Hood <[email protected]> wrote: > Hi everyone, > > I found that if a line touches itself, if I use the vector overlay "clip" > algorithm on that layer, the feature gets broken up into 3 pieces (I can > tell by running it through the "multipart to singleparts" algorithm). > > See the screenshot below of some example inputs, and I've attempted to > attach the layers. If I run the line layer through "multipart to > singleparts" it produces a layer with only one feature. But if I use the > polygon to clip the line layer, and then run it through "multipart to > singleparts" it gets split at the point where it touches itself, into > three pieces. > > I haven't been able to find a tool for validating or repairing geometries > that thinks there is a problem with the original geometry, so I think this > is a bug with the clip algorithm. Should I file a ticket? > > Or should the original geometry be considered invalid, so I can't expect > the algorithm to preserve it as a single feature? If that's the case do we > need a better tool for validating or repairing geometries, which can > identify geometries with this problem?). > [image: image.png] > > Regards, > Alister > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >
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