I have a set of points grouped and enclosed by a Concave Hull polygon as in this question. Within an outer boundary that encloses all the polygons I would like to make these polygons contiguous, that is individual polygons should expand so that each polygon shares edges with its neighbours or the enclosing boundary. Is this possible? I am using QGIS.

This what the original polygons look like:

Concave hull polygons

This is an approximation of what I want, the rules are that the number of polygons should stay the same and that all points that originally were in a particular polygon, should remain within the altered version of that polygon.

Tessellated polygons

Kadir's original solution works well but left a couple of artefacts.


The updated answer resolves this problem.

  • 3
    Can you add a screenshot of your map? It may help people visualize the problem better.
    – Techie_Gus
    Feb 26, 2021 at 9:40

1 Answer 1

  • First, use one of Densify tools (Densify by interval or Densify by count) suitable for you to add additional vertices on polygons' edges.
  • Extract the vertices to points using Extract vertices tool.
  • Create Voronoi polygons using these points. (Voronoi polygons tool) > Layer_A
  • Add a field (POL_ID as an example) to Voronoi polygons (Layer_A) to indicate intersecting Concave Hull. (Join attribute by location tool) > Layer_B
  • Use Dissolve tool to combine polygons in Layer_B by POL_ID.
  • It works fine, but leaves a few artefacts, probably not too many to edit manually, but would be nice to get rid of those as well. Feb 27, 2021 at 15:30
  • @KobusHerbst What is unit of data? m/inch or degree? Feb 27, 2021 at 15:47
  • It leaves artefacts because of the small number of points. So, I've edited the answer. I think it works now. Feb 27, 2021 at 16:03
  • Thank you that solved the problem Feb 28, 2021 at 3:18

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