Using Check Geometries plugin for polygons in QGIS?

Question

I've a few hundred polygon features with many duplicate nodes, gaps, overlaps and other geometry errors. Fixing all errors seems to be quite tricky. I had to run the duplicate nodes check twice to fix all duplicate nodes. After fixing minimum angles between segments (< 1,000000 deg) new duplicate nodes appear. The gap check isn't working because of a topology exception

Input geom 0 is invalid: Self-intersection at or near point ...

but the self intersection check doesn't report any results. Fixing sliver polygons fails for most objects:

Failed to merge with neighbour

What's the best way to use the 'Check Geometries' plugin?

It seems that tiny polygons may be highly problematic in some ways (e.g. polygons with three nodes containing duplicated nodes).

Should I start with a minimal polygon area check?

Answer 1

The problem is generated with invalid geometries, which is not exactly what the geometry checker plugin is analyzing.

At this moment, QGIS has an excellent tool called Fix Geometries, following the method of the ST_MakeValid function of PostGIS.

Once you have all valid geometries, you will notice that the performance of the Geometry Checker plugin, as well as many other components of the platform that also require working with valid geometries, is as expected.

Answer 2

you can solve such problems using v.clean - Toolset for cleaning topology of vector map in QGIS.