Back on the theme of polygons , another common problem is measuring area of 2d and 3D polygons, polygons on an ellipsoid and polygonal meshes (think realistic farm area measurement for a large farm with hills and valleys).
World Wind now has simple sphere based area calculations suitable for roughly measuring countries, states and something of similar scale. I have finally hooked up the calculations to the measuretool display. The goal is still to allow access to the triangulated terrain mesh and calculate areas with known accuracy for personal properties.
The simple area measurement produces passable results for Metropolitan France ( area 543,965 - 551,695 km² according to wikipaedia article) as shown: