- To measure the horizontal angle and vertical angle between two points accurately up to a precision of “1”[ one second].
- To check the alignments of roads, railways track tunnel and bridges.
- It is used in the prolongation of alignment of road, railways etc.
- It is used for measurements of bearing and measurements of horizontal and vertical distances and determination of the direction of true north.
- A telescope which can rotate or transit through 360° about a transverse horizontal axis.
- The bearings for this horizontal or trunnion axis are mounted in two vertical pillars or standards.
- The standards are mounted on a horizontal upper plate.
- The upper plate rotates through 360° about a vertical or alidade axis, the bearing for the alidade axis is mounted in a lower horizontal plate.