Calculate Areas giving negative values

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10-25-2013 10:11 AM
MarceloLago
New Contributor III
Hi,

The calculation of areas on the attached polygon shape file gives negative values. I am using ArcMap 10 service pack 5.

Is this a bug?

Thanks, Marcelo.
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2 Replies
CarolaEklund1
New Contributor II
Hi Marcelo,

one of our users had the same problem a while ago. If I remember right, one cause could be that the polygons were digitzed in a counter clockwise direction; it's also possible that the polygon features are (self) intersecting. (or a combinationof both?)
I think to fix this you will have to run the "Repair Geometry" tool (ArcToolbox -->Data Management Tools -->Features -->Repair Geometry). Select your polygon shp file/feature class as "Input Features". (in our case we also unchecked "Delete Features with Null Geometry")
Hope that helps!

Carola
MarceloLago
New Contributor III
Thank you Carola, repairing the geometry worked fine.

The absolute values of the calculated area were accurate. ArcMap just assigned negative values when "incorrect ring ordering". I guess this would be an easy fix for the developers. 🙂

Thank you again, Marcelo.
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