Tacheometry (/ˌtækiˈɒmɪtri/; from Greek for "quick measure") is a system of rapid surveying, by which the horizontal and vertical positions of points on the Earth's surface relative to one another are determined using a tacheometer (a form of theodolite). It is used without a chain or tape for distance measurement and without a separate levelling instrument for relative height measurements.
Instead of the pole normally employed to mark a point, a staff similar to a level staff is used in tacheometry. This is marked with heights from the base or foot, and is graduated according to the form of tacheometer in use.[1]
The ordinary methods of surveying with a theodolite, chain, and levelling instrument are fairly satisfactory when the ground is relatively clear of obstructions and not very precipitous, but it becomes extremely cumbersome when the ground is covered with bush, or broken up by ravines. Chain measurements then become slow and liable to considerable error; the levelling, too, is carried on at great disadvantage in point of speed, though without serious loss of accuracy. These difficulties led to the introduction of tacheometry.[1]
In western countries, tacheometry is primarily of historical interest in surveying, as professional measurement nowadays is usually carried out using total stations and recorded using data collectors. Location positions are also determined using GNSS. Traditional methods and instruments are still in use in many areas of the world and by users who are not primarily surveyors.
- ^ a b One or more of the preceding sentences incorporates text from a publication now in the public domain: Airy, Wilfrid (1911). "Tacheometry". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 26 (11th ed.). Cambridge University Press. pp. 341–344.
