Electronic Total Station - Precision Measurement Device | Dual Measurement Capabilities, Integrated Prism Target System, Swivel Lens Mechanics

A Electronic Total Station is a electronic device which combines the ability to measure a position horizontally and vertically at the same time. It has two parts, a machine mounted on a static tripod, and a prism mounted in a casing marked as a a targeta on a metal staff which is moved around the site. Total stations developed in civil engineering, but like many other items of equipment, archaeologists realised their usefulness for archaeological purposes.

The tripod-mounted machine part is set up at a a base stationa , often a point from which as much as possible of the survey area can be seen. Several base stations may be needed to cover a survey area; it is always best to have at least two so that some measurements can be taken from both to test for accuracy. The prism is carried around the site and positioned vertically at recording points. It is set at the same height as the machine on the tripod, this is then subtracted to give a a reala height on the ground surface. The person with the prism, rather than the person working the machine, is responsible for what gets recorded.
The machine part of the Total Station has a lens rather like a telescopic with cross-hairs which are focused on the prism. The whole instrument swivels horizontally and the lens swivels vertically too. The Total Station is partly based on a principle used in traditional theodolites, where two 360 degree scales, one vertical and one horizontal