topic Re: Area calculation per continent, projection issue in ArcGIS Pro Questions

Area calculation per continent, projection issue

IroGeorgopoulou — Tue, 19 Oct 2021 07:08:00 GMT

Hi everyone!

I have reclassified a raster layer into a 2-class polygon layer and I need to calculate the area of these 2 class polygons. This has to be done in continent level (how many square km of class 1 are in Europe for example).

I have done it through calculate geometry. My questions are, if the "calculate geometry" tool gives a reliable result when it deals with so large areas and if I have to do the calculation in the specific projection I use per continent. The projection I use for each continent has an impact on the calculated area or it is irrelevant so I can do all calculations in the same world projection? For the world projection I use the Robinson and for every continent I use different (for example I use North_America_Albers_Equal_Area_Conic for N.America)

Thanks in advance!

Re: Area calculation per continent, projection issue

JayantaPoddar — Tue, 19 Oct 2021 07:55:45 GMT

I would suggest you to calculate Geodesic Area, since it considers Earth's curvature and gives you more accurate area.

Calculate Geometry Attributes (Data Management)—ArcGIS Pro | Documentation

or using Calculate Field like

!shape.geodesicArea@squarekilometers!

Re: Area calculation per continent, projection issue

IroGeorgopoulou — Tue, 19 Oct 2021 08:14:52 GMT

Thank you very much for your reply. Yes, I have used this tool to calculate Geodesic Area, so I suppose it is correct.

In the "calculate geometry attibutes", in coordinate system I used the WGS_1984_Web_Mercator_Auxiliary_Sphere and Robinson projection for all my calculations in all continents. My question is, if due to distortions, these calculations are not reliable and I have to use each continent projection for area measurements. Or if it is irrelevant and using the same coordinate & projection system for all continents is correct.