Hi Jo / Oshyan,
I have just trialed Global Mapper and exported an area approx 10,000m square as a Terragen Terrain File. I then started a new TG project, first of all deleting the default Heightfield Shader, and adding a Heightfield (Load file) shader. I selected the .TER file and then added an operator (Heightfield Resize) to the Load node. I ended up with a flat 10,000m square area with no features. I am probably being dumb, but any help would be welcome. I have attached the .TGD, but not the .TER as it is too large.
Many thanks,
Jonathan.