Simviation Forums

I was just wondering if anybody knew how companies make the satellite imagery based textures for flight sim. I understand that they simply replace the world textures but I guess my question is how do they know which textures cover which area? Surely they don't sit there and just start opening every single texture file figuring out which is which? Do they just replace the textures? Or do they make whole new BGL files for the region they're remaking. I was just wondering how all this works after seeing the Google Earth thing in the FSX forum. Enlighten me please  ;D

Thanks!

The scnery in FS is based on landclasses, so if a area has class one then the program would draw texture for example. So they basicly make a completely new scenery that go's over the old one. As far as i know they dont replace anyting, maby remove.