I'm creating a 2D realistic RTS (Real time strategy game) and I wanted to be able to use real locations as the scenarios for the games.
The game will be developed via unreal engine which uses c++. The idea is for the engine to read an file and convert into a grid where each square has type of terrain associated, like in this image of a scenario editor.
It would be preferable if the information was free.
The problem I'm facing is obtaining the information about the different features that influence units or line-of-sight. More specifically I would like to know the information about bodies of water present, roads, elevation (for this i'm thinking of using the google API), forests, etc in a map
I'm just asking for a pointer to an information source. Where can I download or obtain a GML or similar with this geographic information?