The level instrument is set up on a tripod and, depending on the type, either
roughly or accurately set to a leveled condition using foot screws (levelling
screws). The operator looks through the eyepiece of the telescope while an
assistant holds a tape measure or graduated staff vertical at the point under
measurement. The instrument and staff are used to gather and/or transfer
elevations (levels) during site surveys or building construction.
Measurement generally starts from a benchmark with known height
determined by a previous survey, or an arbitrary point with an assumed