Reichenbachfäden
As Reichenbach yarns are two horizontal strokes in the reticle denotes a telescopic tube which, in conjunction with a bar on the approximate distance measurement are used. They were first installed in a theodolite by geodesist and precision mechanic Georg Friedrich von Reichenbach around 1800 .
If the two lines (formerly spun threads ) are attached at a mutual angular distance w = 34.38 arc minutes (tan w = 0.01), then the section read off in centimeters on the measuring stick corresponds exactly to the distance in meters . For experienced observers, the accuracy is about 0.1% of the distance. If an inclined distance is measured instead of a horizontal one , the elevation angle must also be taken into account.
In the thread network of most theodolites, a second pair of Reichenbach threads (vertical) is attached in order to be able to use a possible horizontal measuring basis for distance measurement.
The Reichenbach rangefinder, developed around 1810, can also be used for inclined sights . The theodolite-like instrument allows the exact measurement of the elevation angle and was developed in the Mathematical-Precision Mechanical Institute by Reichenbach and Josef Fraunhofer . From around 1820 it was produced by "Utzschneider and Fraunhofer in Munich" .
See also
literature
- Franz Ackerl : Geodesy and Photogrammetry Volume I: Instruments and Methods of Measurement, G. Fromme-Verlag, Vienna 1950.
- Heribert Kahmen : Surveyors . 18./20. Edition, De Gruyter-Verlag Berlin 1993 and 2005