Why 'Y' parameter?

Why does TerrainY need a Y parameter?

surely it would just return the Y value for the terrain at x,z coords???

I've been wondering the same thing. I just put 0 for the Y parameter whenever I use it ;)

I believe that is there just for balance in that function.
TerrainX has X and TerrainZ has Z.
Probably all 3 use the same C code only returning a different paramater.

For want of not repeating, I just stick a 0 in the Y paremeter.

I did have a snippet of code that went something like:

Altitude=(EntityY(Ship,1)-(TerrainY(Terrain,EntityX(ship,1),(EntityY(Ship,1)),EntityZ(Ship,1)))

This was giving some rather odd readings, until I did as suggested, and put a 0 in...