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I am trying to return the areas of the red polygon that fall outside of the orange polygon, using the difference tool.

Both are vector layers I created by drawing around a georeferenced map. Their attribute tables only contain their area, shown below.

When I run the difference tool, it returns "Feature has invalid geography", and the resulting layer is empty and does not appear on my map.

  • 1
    If you're sure the CRS are the same, there's a vertical line on top of the left orange area that might be source of "invalid geometry"?
    – gvanhavre
    Commented Jun 11, 2021 at 9:37
  • Yeah thats a result of a misclick when drawing the polygon - is there any way to remove it without redrawing the whole polygon?
    – Stuey17
    Commented Jun 11, 2021 at 9:56
  • But also I get the same results when using a polygon that overlaps only the bottom part of the red polygon
    – Stuey17
    Commented Jun 11, 2021 at 10:02

1 Answer 1


Fix geometries: (Processing toolbox -> Vector geometry -> Fix geometries)

This algorithm attempts to create a valid representation of a given invalid geometry without losing any of the input vertices. Already-valid geometries are returned without further intervention.

Then try Difference

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