Deleting sliver parts of single polygon using QGIS

Question

The polygon highlighted in red is a single polygon that has slivers directly attached to it.

I used the Difference tool on two polygon layers which lead to slivers / fuzzy polygon parts (see picture). I saw Deleting sliver polygons after difference operation in QGIS? and got rid of the sliver polygons that are not connected to bigger polygons (black lines and the small polgon on the house). However, I want to get rid of the sliver that is connected to "proper" polygons as well. The red lines that branch out from the one bigger polygon are an example of that. Since I work on datasets that cover an entire county, I need a solution that can be done in a reasonable amount of time.

Is there a way to get rid of these connected sliver polygons?

Some more background information: Layer A contains areas that I want to exclude from layer B. I tried both, extract by location ("touch" and "disjoint") which excluded many polygons as they were slightly overlapping. Couldn't find a good solution for that. Then I tried the method described above and got said problem.

Answer 1

Add a check for polygons with an area below... let's say 30 sqm to your workflow (select by expression using area($geometry) < 30). Maybe 10 sqm, depends on your dataset. Select those, delete those.

Answer 2

No real solution has been found yet, but I got a workaround that worked quite nicely.

1. I got rid of slivers around polygons in QGIS after a Difference tool by first buffering the feature by 5cm. For my case a slight inaccuracy in area was less important than getting rid of the "Difference slivers".
2. The Difference tool also created some unwanted small polygons, some of them slivers but not all. I used the "Multipart to single parts" tool to separate the small polygons as good as easily possible and then calculated their roundness and recalculate their area. Also calculating the number of inner rings (holes) helps filtering out bigger polygons that have a high roundness value (num_interior_rings($geometry)). Lastly the "Extract by expression" tool allowed me to filter out polygons under 50sqm with a roundness of 50 or more (1 = perfect circle; the bigger the less round the polygons are).

That way I didn't get rid of slivers that were attached to polygons that were wanted, but I eliminated as much of them as plausibly possible, I think.

Answer 3

You can do the steps below:

1. use "Multipart to singleparts"to divide the shape file into single parts
2. then select the part(s) that you want
3. export the selected feature and save it!