Instrument height

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As instrument height in which is Geodesy and related measurement techniques, the height of the theodolite (or the meter) above the bottom point ( measuring point ), respectively.

It refers to the intersection of the tilt axis with the vertical instrument axis (standing axis) and is based primarily on the body size (eye level) of the observer, sometimes also on external requirements (bumps, visures , viewing windows in the vegetation ).

For a pure position measurement (only measurement of horizontal angles and flat distances), the height of the instrument is mathematically irrelevant, but it is essential for height measurement . It is usually measured on the scale of the range pole . For precision or technical leveling on sloping roads, a large instrument height is advantageous for two reasons: firstly, to enable the same length of view of the measuring stick both ahead and back, and secondly, to avoid major refraction anomalies near the ground. The latter occur v. a. when the terrestrial refraction is reduced or even reversed by warm air layers just above the ground.

Target height

When calculating height differences , the instrument height is only included with its difference to the target height , which is usually written as IZ .

The target height is the height of the targeted point above the ground or above the point to be measured. To simplify matters, the laser reflector can be attached to the ruler exactly at instrument height so that IZ becomes zero.

See also