Azimuth measurement
The term azimuth measurement includes the astro-geodetic methods for the absolute determination of direction on survey points . They are made by measuring the angle between a star and a well-marked terrestrial target - or high point , for which a theodolite is generally used.
Because of the apparent movement of the celestial body in the sky, an exact time measurement must also be made when aiming at it , and the coordinates of the position are necessary for the calculation .
Instead of measuring angles , star passages can also be observed in the vertical plane of the target point, for example with a passage instrument .
The azimuths obtained relate to the astronomical north direction and are therefore absolute directions. Together with the gyro azimuths , they are therefore also referred to as absolute orientation methods .
The main procedures are
- the solar azimuth (angle measurement between the center of the sun and the target point)
- the polaris azimuth (angle measurement with the pole star)
- the Embacher method (star observation in the largest digression )
- the riveting hammer method (passages of star pairs in the vertical of the target point)
- the circummeridian method.
Solar azimuths are quick and possible during the day, but only moderately accurate (2–10 "depending on the effort). The other methods can reach around 0.1 to 1". In (3) the latitude is determined at the same time , in (4) possibly also the geographical longitude or the sidereal time .
Important applications of the procedures are
- the exact orientation of surveying networks or polygons to the north
- monitoring slow movements of the earth's crust
- the determination of Laplace azimuths for national surveying
- Alternative for the east-west component of the perpendicular deviation .
literature
- Karl Ramsayer : Geodetic Astronomy (= Handbook of Surveying. Vol. 2a). 10th, completely revised and restructured edition. JB Metzler-Verlag, Stuttgart 1970.
- Gottfried Gerstbach : For azimuth measurement with second theodolites. In: Austrian Journal for Surveying. Vol. 71, 1983, ZDB -ID 240968-9 , pp. 53-68.
- Albert Schödlbauer : Geodetic Astronomy. de Gruyter, Berlin et al. 2000, ISBN 3-11-015148-0 .