Merging polygons based on distance in QGIS

Question

How can I merge not overlapping polygons? I'm trying to set up a model that merges polygons that are within 500m from each other, at the closest edge of the polygon.

I have tried with the shortest line between features, but don't know how to extract the length from the line and add it to the polygons so to try to use the merge polygon feature if possible.

is there an easier way?

I was looking for something like aggregate polygons that you find in ArcGIS. Figured I could use join attributes to the nearest directly on the polygon and then remove duplicated.

Answer 1

It is not in QGIS, but if you can run standalone python scripts you could try the (new) dissolve_within_distance feature of geofileops.

It offers a basic subset of features of "aggregate polygons", but it sounds like it supports what you are looking for.

import logging
import geofileops as gfo

if __name__ == "__main__":
    # Init logging so progress printed by gfo is shown
    logging.basicConfig(level=logging.INFO)

    input_path = "/path/you/like/zones.gpkg"
    output_path = "/path/you/like/zones_dissolved.gpkg"
    gfo.dissolve_within_distance(
        input_path=input_path, output_path=output_path, distance=500
    )

Disclaimer: I am the developer of geofileops.

Answer 2

Do you mean 500m from the closest points of two polygons, or centroids?

What about using buffer? You could create a layer that adds buffers of 250m based on your polygons. Then all buffer polygons that touch should be merged.

Then, one would need to keep track of which polygons in the buffered layer are merged and do a corresponding merge in the original layer, which would then be multipolygons.

Sorry if the answer is a bit unclear, it is just an idea of what you could try.