[paradoxharbinger]

if i had to wager a guess, ruggedness is how jaggy the terrain is and would refer to the underlying function that generates the heightmap. the more rugged, the less smoothe it is.

if you look a little into fractal terrain generation it would explain a good deal about how the dom3 mapgenerator works. i don't have time to go into it now as i'm at work, but if no one else has addressed your question to your satisfaction i can explain in greater detail later.