Right, I've done all this. Problem is the base isn't actually in the geoscape terrain from the game's perspective.. if you don't expressly reference a terrain in the ruleset, you get Mars terrain, every time. If you do, you only get the manually set terrain. ie it's impossible to get the terrain from a base location, unlike a UFO. I'm guessing, maybe wrongly, that I'm not the first to try this.. would be nice if the base could cross reference it's Coordinates with geoscape terrain