I was wondering if anyone knows what is the math calculation behind the Add Surface Information tool to extract the Surface Area value for a DEM in raster format.

At first I thought it used it the slop angle and cosine rule to provide the Surface Area. But after implemented this calculation on modelbuilder I discovered that the results I was getting on modelbuilder were very different from the ones I had at Add Surface Information.

If someone have any ideas it would be great.

Thanks,

Gabriel

very different.... examples? perhaps one is in a mix of geographic and planar coordinates? and the other is using projected data with XYZ in the same units? perhaps XY are in meters and Z is in feet?