Step 1: The amount of error (e) associated with the observation is determined from
e = h
h ' = (a
Step 2: The error e occurs in a distance of D = D2 - D1. Assuming the error e is positive and the line of sight is inclined upward, the error in distance D2
Step 3: Calculate the correct staff reading at the distant peg as
Step 4: The capstan screws at the top and bottom of the diaphragm ring is then loosened and the ring is moved vertically so that the line of sight intersect the distant staff at d'.
Step 5: To check the adjustment, read the staff reading on the near peg and it should read
If the near staff reading is not c', then repeat Step 4 and till Step 5 is satisfied.
This method is known as two peg method. In this method, due account need to be taken about sign throughout the test.