instrument used in surveying to measure the height of distant points in relation to a bench mark (a point for which the height above sea level is accurately known). It consists of a telescope fitted with a spirit level and, generally, mounted on a tripod. It is used in conjunction with a graduated rod placed at the point to be measured and sighted through the telescope. The theodolite (q.v.), or transit, is used to measure horizontal and vertical angles; it may be used also for leveling.