There are several applications where one might need to detect the height above the closest "walkable" surface at a position. One such application would be to create a "landing pad" for helicopters on top of another object.
Using lineIntersectsSurfaces is not an option because it doesn't support the "roadWay" lod.
The only solution at the moment is to:
1. Create a test vehicle
2. Transfer the test vehicle to the desired coordinates using setPosXXX
3. Using the (getPos _vehicle select 2) command to return the height above the surface.
If there was a built in command that could return the same result without any need to create a unit, it would be more convenient and hopefully faster, because getPos has a relatively high execution time (~0.01-0.02 ms) which is even worse when combined with the whole process above.