[Qgis-user] Self Intersections: Issues with Polygon Features

[Stijven, Jeroen]

Dear Werner,

Thanks a lot for the helpfull information, but can you send me a screenshot as example please?
Thanks a lot.


Met vriendelijke groeten,


Jeroen Stijven                      E: jeroen.stijven at besix.com

Designer                          Besix Connect nv | Baaikensstraat 21/1, 9240 Zele

+32 493 02 46 91                    W: www.besixconnect.be

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From: QGIS-User <qgis-user-bounces at lists.osgeo.org> on behalf of Nigel Berjak - General via QGIS-User <qgis-user at lists.osgeo.org>
Sent: Thursday, July 3, 2025 5:20 PM
To: Isenmann, Werner (RPF) <Werner.Isenmann at rpf.bwl.de>
Cc: qgis-user at lists.osgeo.org <qgis-user at lists.osgeo.org>
Subject: Re: [Qgis-user] Self Intersections: Issues with Polygon Features

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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



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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<mailto:Werner.Isenmann at rpf.bwl.de>



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