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I have coordinates in decimal degrees and need to calculate area for polygon objects. I tried to use AreaCalculator and set up criteria to find all these bigger than 100 sqm. But result is not as I expected. Should I convert first from decimal degree to metric?

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use a reprojector on your data before your AreaCalculator to convert to Meters - WORLD-MERCATOR would work - then reproject back. – Mapperz Jul 11 '12 at 13:47
up vote 8 down vote accepted

Yes, reproject but use _AZMEA_ as the coordinate system. It's a dynamic equal area projection designed exactly for this. Then simply reproject back. In future the AreaCalculator will have an option to do this reprojection automatically.

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