Levelling can be divided into two main categories: Area levelling and Series levelling. Area levelling is employed when the points to be levelled are in an area where they can be observed from one instrument station as shown in the diagram on the right.

1. The level is set up in a convenient location and levelled up (at a point where all the points to be measured can be seen ).

2. A Backsight(BS) is taken to a Bench Mark (BM) or TBM and a staff reading observed to the nearest 0.001 (1 mm ) and booked. The shot 'R' in the diagram.

3. The Back sight reading is then added to the RL of the BM to give an RL for the instrument axis - called the Collimation Height or Instrument Height (IH).

4. The staff is then moved around to a succession of points, called Intermediate points, where the staff reading is observed to nearest 0.001 or 0.01. Example.

5. The RL of the intermediate point is determined by subtracting the staff reading from the IH level.Example.

6. Once observations have been completed to all intermediate points, the last reading is taken back to the BM or TBM - called the Foresight (FS). This last reading should always be taken to another point of known RL if possible.

7. The observations are then reduced to give an RL at each of the observed point. Observations can also be reduced using the Rise and Fall method if desired.

! A check on the work can be carried out by moving the instrument to another location and re-observing all the intermediate points again.