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I have a simple polygon shape (single part, no holes, etc.) that has been imported (into a personal geodatabase) from third-party data (originally DWG and XML) that somehow has a SHAPE_AREA with a negative value. I am assuming that the problem is caused by how it is imported (or the files it is imported from), which I have no control over. Within ArcMap I have attempted to replicate the issue, but I have not been able to create a negative area polygon in my attempts.

Enter image description here

So far, the only way I've been able to find to change the negative to positive is to create a new polygon by tracing the existing polygon, then copying all the attributes across and deleting the existing one.

However there are potentially others that have been imported (or would be in the future) like this, and to trace each and copy attributes would be very time-consuming and has the potential to introduce errors.

How can I force my area to correctly show a positive value here? I don't mind if it's by creating new features and deleting the old, or by somehow reversing the polygon so that ArcMap calculates the area correctly - it just needs to be efficient and not introduce new errors.

What I've tried:

  • Copy/Paste the existing feature (didn't correct the area)
  • Tracing the existing feature (produced correct area, but has potential for errors, and is time-consuming)
  • Clicked on Edit Vertices and right-click on feature to "Flip" (Flip wasn't available on a polygon)
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  • In shapefiles the outer ring of a polygon must wind clockwise. Obviously in your imported polygon it winds counterclockwise.
    – user30184
    Commented Jul 6, 2021 at 18:56
  • @user30184 thanks for the comment - these are in a Personal Geodatabase, not a shapefile. I don't believe shapefiles were used anywhere in the process (but I could be wrong).
    – Midavalo ♦
    Commented Jul 6, 2021 at 19:01
  • ESRI probably uses similar way to construct geometries in Personal Geodatabase than in shapefiles and the error message anyway tells that the error was in clockwise/counterclockwise ordering Repaired Feature 1 because of incorrect ring ordering.
    – user30184
    Commented Jul 7, 2021 at 9:10

1 Answer 1

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Right after posting this question I remembered the "Repair Geometry" tool in ArcToolbox

ArcToolbox > Data Management Tools > Features > Repair Geometry

All I had to do here was point the tool to my layer and hit OK (there are no other options other than "Deleting features with Null geometry" which I left unchecked)

The tool ran quickly and returned the following message:

Repaired Feature 1 because of incorrect ring ordering

Upon reloading my layer the SHAPE_AREA now shows the correct positive value.

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