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?
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.