Using this file you can create your map from scratch or import and change existing maps.
The editor is implemented as Excel workbook. With YAME you can create your map from scratch or import and change existing maps.
If you look for a tool that generates maps based on satellite photos have a look at 'BMP to WBC Converter'. Should you need a tool to create random maps according to parameters then 'Atlas' might be the correct choice. YAME is for you, if you need an editor that let you set and modify each and every tile on a map and generate a ci4WorldBuilder file to play that map in Civ4.
The map can be of almost any size (max 255 columns - Excel restriction), contain height information, different terrain types, features, bonus tiles and rivers. Up to 18 Cvilizations may be placed.