Okay, I probably found out how the ground is formed.
I highlighted one unmodified section of mesh which seems to represent vertices. Each section at the header start (haven't checked much further) seems to contain 9 vertices which are connected to each other. The numbers colored with orange are nullified vertices and then I added hex number 01 to the possible Z-axis variable. This was the result:
It seems to go a little over the ground which is expected with 01 value since it's the first bit to represent the shortest distance in this 3d dimension. Also the XY-axis seems to collide in the middle which is also expected since they are 00 00 both now.
Here's a little clarification how it may work:
Offset: 0x3dd8
B3 F3 B3 F3 00 00
B3 F3 CD F7 00 00
B3 F3 E7 FB 00 00
B3 F3 00 00 00 00
B3 F3 1A 04 00 00
B3 F3 34 08 00 00
B3 F3 4E 0C 00 00
B3 F3 68 10 00 00
B3 F3 99 EF 00 00
X-axis, Y-axis, Z-axis
X and Y axis may differ.
So to sum up it seems that each vertices has 6 bytes reserved where 2 bytes represents axis in XYZ-format. Hope this gives some insight for you MakiPL!
EDIT: I tested it with a0stg101.x and this is what I got (sorry for bad angle, maybe we can get better angles when we can alter the camera):
This is what i changed:
Seems to work how i described it. I'm tired now so going to sleep :/