[Qgis-user] QGIS Simplify polygons without creating gaps and overlaps

[Jochem Kail]

After searching a bit more, I found a very good solution myself (but of 
course many thanks for all other helpful replies) and I wanted to share 
this in case anybody was or will have the same problem: Of course, there 
is the GRASS tool "v.generalize 
(https://docs.qgis.org/3.44/en/docs/training_manual/processing/generalize.html). 
I learned that GRASS is a true vector model, meaning that instead of 
storing independent, overlapping polygons (like simple features do), it 
builds areas from shared boundaries. Therefore, when simplifying or 
generalizing polygons, the resulting simplified polygons still share 
their boundaries and have no gaps and overlaps. Moreover, GRASS 
v.generalize offers different simplifying algorithms. By setting the 
maximum tolerance value a bit larger than the cell size of the raster 
the polygons originated from (e.g. 12m for a 10m raster), the zig-zag 
polygon borders are replaced by straight segments. This is exactly what 
I was looking for.

Am 12.06.2026 um 19:58 schrieb Jochem Kail via QGIS-User:
> I polygonized a land use raster layer using GDAL – Raster Conversion – 
> Polygonize (Raster to Vector). The borders of the polygons of course 
> exactly follow the borders of the raster cell. In ArcPro, there was an 
> option to create simplified polygons when polygonizing raster data. I 
> tried to find a similar tool in QGIS or a way to simplify the polygons 
> resulting from Polygonize, but did not find any solution that does not 
> produce gaps or overlaps.
>
> Any suggestions are greatly appreciated, thanks!
>
-- 
sent from my R2 unit
-------------------------------------------------------
Jochem Kail
Dr. rer. nat.
University of Duisburg-Essen
Faculty of Biology
Department of Aquatic Ecology
Universitätsstrasse 5
D-45141 Essen
Germany

Room S05T03B08
Tel: +49.201.183.3046
Tel: +49.160.96228374
Fax: +49.201.183.2179

jochem.kail at uni-due.de
https://www.uni-due.de/aquatische_oekologie/mitarbeiter/jochem_kail.php

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