_________ is the correct formula to determine the elevation difference (dZ) between two points on the ground using a total station.
(VD = Vertical difference, HI = Instrument height and HR = Reflector height)
1
dZ = VD - (HI + HR)
2
dZ = VD + (HI - HR)
3
dZ = VD(HI - HR)
4
dZ = VD(HI + HR)