what is theodolite?
A theodolite is a precision instrument for measuring angles in the horizontal and vertical planes. Theodolites are mainly used for surveying applications, and have been adapted for specialized purposes in fields like metrology . A modern theodolite consists of a movable telescope mounted within two perpendicular axes — the horizontal or trunnion axis , and the vertical axis. When the telescope is pointed at a target object, the angle of each of these axes can be measured with great precision, typically to seconds of arc.