Optical plummet is used in a total station is used for accurate centering over a station. It has either a bullseye or cross hair sight for positioning the instrument over a survey marker or ground control point.
The older tribraches required a plumb line to allow them to be positioned vertically over a point and took longer to set up.Some modern total stations have an integral laser plummet built in.
Electronic distance measurement (EDM) is a way of determining the length between two points by looking a phase changes that occur as electronic energy waves, which travel from one end of a straight line to the other.
A total station is an optical surveying instrument that uses electronics to calculate angles and distances. It combines the functions of a theodolite with that of a transit level and electronic distance meter (EDM).
A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure both vertical and horizontal angles and the slope distance from the instrument to a particular point, and an on-board computer to collect data and perform triangulation calculations.
