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I'm a bit stuck on calculating distance between two polygon features (i.e. closest part of the polygon A to closest part of polygon B (not necessarily where the points are as sometimes a line between the points is closest).

I've figured out I need to convert the polygons to points so I've used 'points along geometry' to get points at 10m intervals along Polygon A and Polygon B's boundaries.

However, when I then try and pass these features through things like 'distance matrix' and 'shortest line between features' it gives me a measurement for nearest point in B for every point in Polygon A (resulting in over 9000 entries in the attribute table). I just need to know the distance between the closest Polygon A point and Polygon B point.

If it helps, I'm trying to find the distance between 30 Scheduled Monuments (Polygon A) and the Site Boundary (Polygon B).

I'm reasonably new to QGIS.

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    Are the polygons in the same layer or two different layers?
    – Bera
    Commented May 15 at 18:31

1 Answer 1

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Leave your data as polygons. Use the "Shortest line between features" tool. If your polygons are both in the same layer, set "Maximum number of neighbors" parameter to 2 (otherwise you just get the distance between a polygon and itself, i.e 0). Select (or filter) for distances > 0.

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  • Thanks - guessing I may want to get the polygons to break up into smaller vertices first? Is there an easy way to get QGIS to put more verticies along the polygon boundaries?
    – sarchaeologist
    Commented May 17 at 12:33
  • No. The tool will find the closest point from/to anywhere along the polygon border, which can be between vertices.
    – user2856
    Commented May 17 at 13:19
  • @sarchaeologist if this answered your question, please accept it so the question is marked as answered gis.stackexchange.com/help/someone-answers
    – user2856
    Commented May 29 at 9:18

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