Those are the old terrain commands
You should use the advanced terrain commands instead
Have a look at this commented code:
create_terrain1:
rem heightmap size in pixels
hgtmapsize=128
rem terrain scale up
terrscale=1000
rem terrain height scale
terrheightscale=50
landsize=hgtmapsize*terrscale
rem this is the terrain texture (ground landscape)
load image "L3DT01\L3DT01tex.bmp",1,0
rem this is the detail texture (tiled on top of
rem the land texture according to the tiling command)
load image "L3DT01\grassdetail02ms.jpg",2
rem make the object terrain
make object terrain 1
rem profile it according to the heightmap gray scale - must be true color to work
set terrain heightmap 1, "L3DT01\L3DT01hgt-128.bmp"
rem set the scale (size) of the terrain - (xlength,height,zlength)
rem it equals the heightmap size in pixels multiplied by the scale factor
rem in this case 128 x 1000 = 128000 DBP units
set terrain scale 1,terrscale,terrheightscale,terrscale
rem split value (number of limbs for culling)
set terrain split 1,8
rem detail map tiling
set terrain tiling 1,1
rem light - xdir, ydir, zdir, red, green, blue, intensity
set terrain light 1,0.6,0.6,0.6,1.0,1.0,0.9,0.9
rem texture the terrain with base (1) and detail (2) texture
set terrain texture 1, 1, 2
rem finally build the terrain
build terrain 1
return
then put "update terrain 1" in your Do-Loop