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In QGIS 3.20 I have clusters of overlapping polygons as shown in the image below:

Clusters of overlapping polygons

My requirement is to dissolve each of these clusters into single polygons. While the "Dissolve" tool provides me with the required visual output as shown below, it ends up merging all the polygons (of all the clusters) together into a single feature.

Result when 'Dissolve' is used

The polygons in each cluster don't share a common attribute so I can't dissolve by attribute either. The full set is also too large in number for me to select them manually.

How do I dissolve based on whether or not the polygons overlap with each other?

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  • 1. Dissolve, 2. Multipart to single parts
    – Babel
    Commented May 13, 2023 at 9:10

1 Answer 1

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Let's assume there are nine features in the 'grid_test' (reddish) layer, see the image below.

input

Use the the GDAL's "Dissolve" (GDAL > Vector geoprocessing > Dissolve) from the Processing Toolbox (Ctrl+Alt+T).

Tick the 'Produce one feature for each geometry in any kind of geometry collection in the second source' in Advance Parameters.

dissolve_param

Press Run and get the output like this:

result

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  • First, "Geometry Column name" field can't be "geometry" in your example. It throws an error about not having a field with that name. In any other setting, I could not reproduce the same result as you presented with that algorithm.
    – Güray Hatipoğlu
    Commented Sep 13, 2023 at 14:33
  • What kind of error ?
    – Taras ♦
    Commented Oct 20, 2023 at 19:00

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