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How can I measure the area of a polygon resulting from the intersection of two other polygons? If I use the measure tool or open the attribute table for the resulting polygon, it shows me the areas of the original two polygons...

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Which program do you use? – Jakub Jun 14 '11 at 19:04

You can use the Union tool to create a single featureclass from the two polygons and then calculate the area of each feature within the polygon.

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you mean the "Intersect" tool instead of "union", right?… – julien Jun 14 '11 at 20:30
@jul Correct, but Union does the job too. It also includes the remaining portions of the original polygons. – whuber Jun 14 '11 at 20:48
@jul Either will work, but like @whuber said, Union includes the remaining portions of the original polygons, which may be useful to @Jakub. Both will provide the required area, so it'll come down to the required application. – Radar Jun 14 '11 at 21:08
The crucial point is that @Romina may be using a GIS that does not automatically compute areas, even though it shows "Area" fields among the attributes. Thus you need to calculate the new areas explicitly. – whuber Jun 15 '11 at 3:06
Thanks for the answers. I'm using ARCMap 10. I had been using ArcView 3.2 where I just did the intersection and could later read the area of the resulting polygon. I haven´t been able to do this in ArcMap yet... – Romina Jun 15 '11 at 12:21

Instead of using Field Calculator to calculate area of new polygons that were split by the intersection, create a new field called Area, right click, choose Calculate Geometry. Choose what unit, and it will calculate the 2 new polygons correctly!

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