Tachymeter
Overview
 
A tachymeter or tacheometer is a type of theodolite
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 and rocket launch technology...

 used for rapid measurement
Measurement
Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the metre, second or degree Celsius...

s and determines, electronically or electro-optically, the distance to target, and is highly automated in its operations. Such tachymeters are often used in surveying
Surveying
See Also: Public Land Survey SystemSurveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them...

. A tachymeter scale
Tachymeter scale
A tachymeter scale is a scale sometimes inscribed around the rim of an analog watch. It can be used to compute a speed based on travel time or measure distance based on speed....

 is also used as the name of the scale sometimes inscribed around the rim of an analogue watch, useful in converting time intervals to speed or other rates of events.

Tachymetry or tacheometry
Tacheometry
Tacheometry , is a system of rapid surveying, by which the positions, both horizontal and vertical, of points on the earth surface relatively to one another are determined without using a chain or tape or a separate levelling instrument....

is the process of measuring distance
Distance
Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, or an estimation based on other criteria . In mathematics, a distance function or metric is a generalization of the concept of physical distance...

 indirectly.
 
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