I'll bet someone who's handy with graphics libraries could write a tool that converted satellite images to Civ map files. The basic job of outlining land masses would be easy because it would be just "blue == water." It could get fancy by guessing what type of tile the land is based on its color, but that would be gravy. You'd have to do some work, but it could get you started by doing the most tedious and tricky work. Then you just paint whatever terrain types you think fit within the land mass lines.