Levelling in surveying

Leveling refers to any of the various processes by which elevations of points or differences in elevation are determined.

surveyors taking levels

To measure the difference in height ( ∆ H) between two points A and B, vertical rods are set up at each of these two points and a level somewhere between them.

The height difference between A and B is the difference between the staff readings.

The leveling is opened and closed fro a known point.

Opening a level: it involves setting up the level  a known control point and taking the first staff reading while  the staff is held vertically at a benchmark.


Closing a level: After taking level, the last reading is taken on a staff while held vertically on a benchmark.

Once the elevation of a point is determined, that point can be used for determining the elevations of other points

Below are the common terms used in leveling: 

 Backsight (BS): first reading taken on a staff when the instrument is set up at a new station

Foresight (FS): last reading taken on a staff before the instrument is set up at a new station

Turning Point: A point at which you have established an elevation with FS and on which you will subsequently take a BS

Intermediate sight:  A foresight to a point at which you want to know the elevation but which will not be used as a turning point