Quote Originally Posted by Lysander
I was looking at this problem as well. I think it is true that the game uses map_heights.hgt instead of the map_heights.tga. I thought I might have had a way to get around this, see below, but I did not get it to work. sorry.

This is what I tried:
First, if you delete map_heights.hgt and leave the map.rwm file intact, then the game will still load and work fine (so technically you don't need the height file). Now, if you are making a new map you would not have the map.rwm to use as a replacement for map_heights.hgt. So, secondly, to solve this problem, use a separate installation of RTW (pre 1.3) to generate the map.rwm file. Lastly, port the new map.rwm file into your RTW 1.3/BI installation, using it as a replacement for map_heights.hgt (i.e., delete it).

After doing some experiments it seems that the map.rwm files from RTW 1.2 are not compatible with RTW 1.3.
The fact the map.rwm from 1.2 doesn't work anymore for 1.3 makes me think that the .exe has the ability to generate .hgt files from .tga, like it does with the sprites. Now we need to know the proper command. Maybe Jerome would oblidge like he did for the sprites.