Because atm, the map dimensions have to be a power of two. 40x40 is between 2000x2000 and 4000x4000 in heightmap size. The lower memory use is because of the changed way of texturing. The limit really is defined by spring itself, the map renderer uses little memory in comparison with the rest of spring. But maybe that can be optimized later.But if the new format is supposed to use less memory, why is there a lower max size due to memory restrictions???
OTA scale has no meaning in my map renderer, heightmap size is the standard unit for map size. You don't see Chris Taylor using OTA scales either.In future please use OTA scales rather than heightmap scales unless you're willing to put up a conversion scale (this many heightmap pixels == this many OTA sized units e.g. a 20x20 map is this many by this many)
I've said earlier that extremely bigger map size wasn't really my goal. Big maps suck. The bonus comes from being able to use the all the cool shading technology on the map texturing.