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Is there a way to calculate the area of overlap between features (polygons) from the same feature class. See figure below as illustration for example. There are 3 features with an ID and area and I want to calculate the area where 1 overlaps with 2, 1 overlaps with 3, and 2 overlaps with 3. The idea is to get a sort of cross-validation table with polygons 1, 2 and 3 across each row and column with the diagonal as 1 (i.e. 100%) and the off diagonal as the proportion overlap with other polygons. Keeping in mind that this is all one feature class or shapefile. I'm thinking the Identity tool in ArcGIS ...

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    Intersect or Union the layer with itself. Or are you asking for a non ArcGIS solution ("'Im thinking the Identity tool in ArcGIS ...")?
    – Bera
    Commented Nov 19, 2020 at 19:14
  • topology with rule must not overlap can solve your issue.
    – riflo
    Commented Nov 19, 2020 at 19:45
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    Thanks @BERA, I was looking for an ArcGIS solution. Will try out the union with the layer itself and report back, sounds like this will work.
    – Andrew15
    Commented Nov 20, 2020 at 1:24

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I ultimately used the ArcGIS union tool and added the layer in twice under the input, effectively doing a union with itself as suggested by @BERA. I then calculated the area of each unique feature (i.e. row) in the attribute table. The table was then exported to excel where I removed any features that were self overlapping and just kept the features which overlapped with a different feature (all discernable by the feature ID). Using pivot tables I was able to sum up the area of each overlap.

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