MapTool is a small open-source tool designed to apply changes to tile, overlay and object data of map files of Command & Conquer: Tiberian Sun & Red Alert 2 based on pre-defined conversion profiles. It is capable of performing operations such as converting maps from one terrain theater or another.

Anyway, head to this topic to download the tool and its future updates. Be aware that you need Microsoft .NET Framework 4.0 to run it.