Now I face the next problem:
After importing the terrain, the heightfield loader says the terrain is 21605 meters wide , so 21 km.
The actual realworld distance is a little bit more that 500 km.
This affects scale, a lot!
How can I convince terragen of different sizes?
[Edit:]
Found it: Heightfeild resize
Now I realize how enormous this area is, thanks to the atmosphere haze.