Getting a unit's Z Location

I've been trying to make a unit (naval to be exact) which cannot attack units above it. So I've been searching in 'real comparison' for a Z of region, Z of unit position but I haven't found anything.
So is there a function in JASS which returns that value?
I've been trying to change GetLocationY to GetLocationZ in the trigger after changing it to custom text but it crashed my WE while saving lol (luckily the map survived :) ).

Martinez

well, you can get the cliff hieght of a unit, but i dont know how to get how high up on a hill or something a unit is.