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I am trying to compare two polygons to find out how much of their area is the same and now much is different.

I've been trying to use feature compare but keep getting errors. I have been just using geometry and omitting everything but area

error says tables have different number of fields

when I omit all but area the error is the same but says base, 3 test, 1

attribute table for polygon attibute table for polygon

Mairi Teasdale
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    Welcome to GIS SE. As a new user, please take the [Tour]. Please [Edit] your Question to present the error as text in the body of the Question. Images are not legible on all devices, and are not searchable by others with the same issue. – Vince Jul 11 '22 at 12:06
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    Use the Union tool instead and make sure polygons from dataset A have a different set of unique ID's than those of dataset B. Then you will be able to determine what has become what, and what has ben lost. – Hornbydd Jul 11 '22 at 13:42
  • how would i interpret the output of the union tool? looking for area that is just polygon A, area that is just Polygon B and area that is both? @Hornbydd – Mairi Teasdale Jul 11 '22 at 13:55
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    try running the tool and look... – Hornbydd Jul 11 '22 at 14:07
  • @Hornbydd why didn't i think of that – Mairi Teasdale Jul 11 '22 at 14:13

2 Answers2

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I didn't use the Feature Compare tool before, but here is a possible alternative solution to find the same area between the two polygons if they are not in the same feature layers.

You can use the Intersect tool. Put your two polygon layers into the Input Features (ranks don't matter in this case), leave other settings as default, and click Run. Then, you will get a new polygon layer, which is the common/same areas of the two original polygons.

Yilin Lyu
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The 'Union' tool is very useful for this sort of thing. See: https://pro.arcgis.com/en/pro-app/2.8/tool-reference/analysis/union.htm

The resulting feature class will include all the attributes of both of the input feature classes, PLUS two 'FID_XXX' attributes - one for each of the FIDs (OBJECTIDs) of the original feature classes.

The areas that cover one of the input polygons but not the other will have the original FID (OBJEDCTID) of the relevant polygon input in the relevant 'FID_XXX' attribute, and will have '-1' in the 'FID_XXX' attribute for the other feature class (that does NOT cover that area).

The areas that are covered by polygons from BOTH input feature classes, will have non-negative FIDs values in BOTH of the 'FID_XXX' attributes.

Son of a Beach
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