[Qgis-user] Vector smoothing (polygons): topology/geometry problems

[Ujaval Gandhi]

My go-to open-source tool for simplifying data and fixing topology issues is
mapshaper [https://github.com/mbloch/mapshaper]. With a single command you can
fix gaps, slivers, overlaps etc. See
tutorial https://www.youtube.com/watch?v=iyDj8AvX3H0
[https://mailtrack.io/l/da99c1253d9a5a1802e17b309f07d2e80211c817?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DiyDj8AvX3H0&u=8747767&signature=b0e19146e5a24474]
---
Ujaval Gandhi
Spatial Thoughts
www.spatialthoughts.com
[https://mailtrack.io/l/f84aa9dae08254f210e6536694029b85c5e443b7?url=http%3A%2F%2Fwww.spatialthoughts.com&u=8747767&signature=ccbe13c41fa147af]




[data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=3D]
On Tue, Mar 18, 2025 at 3:14 PM Stefan Giese (WhereGroup) via QGIS-User
<qgis-user at lists.osgeo.org [qgis-user at lists.osgeo.org]> wrote:


> Hi,
> 
> 
> since QGIS 3.36 there is an new processing algorithm "coveragesimplify" (->
> https://docs.qgis.org/testing/en/docs/user_manual/processing_algs/qgis/
> vectorcoverage.html#qgiscoveragesimplify
> [https://docs.qgis.org/testing/en/docs/user_manual/processing_algs/qgis/vectorcoverage.html#qgiscoveragesimplify]
> ) where no edges will cross or touch after the simplification...it requires
> version of GEOS >= 3.12
> 
> 
> Best regards
> 
> Stefan
> 
> 
> Am 18.03.2025 um 10:23 schrieb celati Laurent via QGIS-User:
> 
> > Dear all, 
> > I performed a raster segmentation from a Spot6 satellite image with OTB. I
> > polygonized/vectorized this raster segmentation in order to get a vector
> > file. To limit the pixelation of this cover, I was thinking of smoothing the
> > layer with the QGIS tool. This works, but the problem is that it generates
> > topology/geometry issues (overlap, holes, etc.). And I can't afford to have
> > invalid geometries. Could you share some advices? Guidances in order to skip
> > those problems? I've attached a screenshot of the smoothed vector
> > segmentation.
> > 
> > Thanks so much.
> > 
> > image.png
> > [https://mail.google.com/mail/u/0?ui=2&ik=f532d47391&attid=0.1&permmsgid=msg-a:r-6003330744555848179&view=fimg&fur=ip&permmsgid=msg-a:r-6003330744555848179&sz=s0-l75-ft&attbid=ANGjdJ9JDUsQqM6Feikf3BNQvhKrU-lTKiCp8duvPNhaFvkMpVW3bmLpzVr584-izw9rvLG-s6kKE4Htyuo7NEE2WLGfgrXzXYyNTzIj82hXgYEqFgI6GDUIS7zNISw&disp=emb&realattid=ii_195a982f65ecb971f161&zw]
> > 
> > 
> > 
> > 
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> -- 
> Mit freundlichen Grüßen
> Stefan Giese
> Projektleiter/Consultant
> ---------------------------------------------
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