hello,
i am trying to calculate area of several polygons using calculate geometry and i am getting the area with negative values. the projected coordinate system is Arc 1960 UTM zone 37S. i cant figure where the problem is. kindly help
1. Take a backup of your data.
2. Run Check geometry.
3. Run repair geometry.
4. Then try calculating area in a new field with double data type.
Karin,
As ArcGIS cannot create invalid geometries (Why do area calculations return negative values?) are your "backwards" polygons being created in another program and being brought into ArcGIS?
Scott
FYI, this happens when your polygon is drawn "backwards". Polygons should be drawn clockwise. If drawn counter-clockwise, you'll have negative areas. There's a similar phenomenon with polylines.
And THANK YOU to Kishor for the solution! I have a dataset created by a modeling software in which half of the polygons (17,000) were drawn backwards. Due to the negative geometry, I couldn't work with the dataset at all.
Karin
Hi BARBARA NJIRU
Could you mark the answer by Kishor Ghatage as the correct one? Thank you.
Kind regards, Xander
Thank you. did run repair geometry and it worked perfectly..
This is caused by incorrect orientation of the polygons rings. As Kishor Ghatage suggests, repairing the geometry will probably solve the problem. If you work with a featureclass in a file geodatabase, you do not need to recalculate the area, this will be done automatically...
Hi Barbara,
It could be a geometry issue.
Try Repair Geometry (Data Management Tools)
Thanks,
Jay
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