Simple Levelling

For finding difference between the levels of two nearby points this is the method used. Given figure shows one such case in which level of A is supposed, say 200.00 m. RL of B is required.

∴          For setting at station Plane of collimation = 200 + 2.7   = 202.7 m

Fore sight on B = 0.80 m

∴          RL of B = 202.7 - 0.80

                         = 201.9 m

It can be noted that the instrument station L1 require not be along the line AB (in plan) and in the calculations RL of L1 do not appear.