I am trying to understand an issue with a relatively simple overlay analysis. I have two polygon feature classes: 1 for my zones (with 1 zone field), and 1 for my classes (no class fields). My global data are all WGS_1984, so I am projecting on-the-fly to get area calculations (Mollweide) in km2.
When I run the "Tabulate Intersection" tool, I get what appear to be accurate percentage values, but very much inaccurate area values. As an easy illustration of the issue, see the example values below for a zone with 100% intersection:
Tabulate Intersection PERCENT: 100%
Tabulate Intersection AREA: 116.2149223 km2
Zone polygon area (from calculate geometry): 96.86654592 km2
Intersect tool area (from calculate geometry): 96.866546 km2
Any clue what is going on here? What am I not understanding about the Tabulate Intersection tool that leads to this discrepancy?