[Qgis-user] Self Intersections: Issues with Polygon Features
Nigel Berjak - General
nigel at s3.co.za
Thu Jul 3 08:20:06 PDT 2025
Hi Werner
An old trick is to buffer using 0 units, which usually resolves
self-intersections.
Cheers.
---
Regards,
Nigel Berjak
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On 2025-07-03 16:11, Isenmann, Werner (RPF) via QGIS-User wrote:
> Hi,
>
> some colleagues have problems with shapefiles (really...) that contain
> polygons with self-intersections. The Vector Overlay - Clip tool, for
> example, cannot be executed because the algorithm does not run due to
> the self-intersection. Before executing the tool, the parameter
> 'Invalid feature filtering' can be set to 'Skip (Ignore) Features with
> Invalid Geometies'. The faulty polygons are then skipped, which is not
> desirable, however.
>
> QGIS offers various options for repairing self-intersections, for
> example:
>
> 1) Vector - Check Geometries plugin: however, this sometimes has very
> long runtimes which might not be acceptable.
>
> 2) Vector Geometry - Check Validity
>
> a - Method QGIS: takes a very long time, or does not run through
>
> b - Method GEOS: works correctly and quickly. However, only the first
> error is ever found. This is not convenient for files with many errors.
>
> Does anyone know a good solution for repairing (many)
> self-intersections with high performance in QGIS?
>
> Many thanks in advance,
>
> Werner
>
> ---
>
> Werner Isenmann
>
> Regierungspräsidium Freiburg
>
> Referat 91 - Geowissenschaftliches Landesservicezentrum
>
> Albertstraße 5
>
> D-79104 Freiburg i. Br.
>
> Phone: (+49) 761 208-3008
>
> E-Mail: Werner.Isenmann at rpf.bwl.de
>
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