How do I determine the Surface Area Units used in the Polygon Volume tool?

Question

I am trying to calculate the surface area inside of a polygon from a TIN which I have generated from a DEM. The Data Frame Projection is WGS 1984 UTM Zone 37S, as is the polygon. The TIN generated from the DEM is in WGS 1984. When I run the "Polygon Volume" tool I end up with the value of 96.248, but I'm not sure what units the SArea is being reported back in.

The UTM coordinates are recorded in Meters, but I know that the surface area is not being reported in meters, as 96 is far too small.

When I tried to project the TIN into WGS 1984 UTM Zone 37S, it no longer matches the location of the polygon.

What am I missing?

AndrewKinzer · Answer

Thank you, Dan and Curtis. Going back to ground zero and re-projecting the DEM into a projected coordinate system did fix the problem.

DanPatterson_Retired · Answer

If your DEM data are in a geographic coordinate system (aka GCS, longitude-latitude), I would project it to a projected coordinate system (Project tool, to UTM) prior to constructing the TIN.  I would ensure that the polygon file is projected to the same coordinate system as well...then try using the tool

curtvprice · Answer

You should set the geoprocessing environment output coordinate system to the coordinate system in which you want the analysis to take place. I'm surprised the TIN and DEM are not in the same coordinate system, when one was generated from the other.. You may want to re-run that process with the output coordinate system set to the same as the DEM.