Astronomical Geodesy

As astronomical geodesy that part of the higher geodesy is called, which deals with the measurement of the earth figure with the help of astronomical objects and derives geodetic reference systems , coordinates and details of the gravitational field from it.

Above all, the methods of geodetic astronomy as well as some of satellite geodesy and cosmic geodesy are used and matched as closely as possible with mathematical-physical earth models .

Specific tasks are the storage and orientation of geodetic triangular networks with the help of astronomical location determination (measurement of plumb line and azimuths ) as well as the astronomical-geodetic network adjustment . The latter is the exact calculation of a larger surveying network , taking into account the vertical deviation on its measuring points, and the introduction of large-scale controls in the national survey (see Laplace azimuth and stellar triangulation ).

If the regional parameters of the earth's ellipsoid are also determined in an astro-geodetic network, then a best-connected ellipsoid (reference ellipsoid) of an entire region or a continent can be derived. Such an ellipsoid adapts itself ideally to the working area, while a middle earth ellipsoid represents the best possible adaptation to the entire mathematical figure of the earth  - the geoid  .

Other important tasks of astronomical geodesy are

• the monitoring of the earth's rotation and its (minor) changes
• the creation of mathematical earth models that are suitable as a reference system for global coordinates or for a national survey ,
• and, based on this, the geodetic datum of a land surveying network - according to the method of translative or projective vertical deviation compensation (terms according to K.Ledersteger). The parameters of the network and the ellipsoid are determined in such a way that the sum of the squares of the vertical deviations in the astronomical measuring points becomes a minimum.
• The astronomical-geodetic geoid determination  - the astrogeoid  - by means of the astronomical leveling (measurement of vertical deviation profiles)
• and (as a transition to physical geodesy ) the modeling of layers of the earth's crust in order to be able to represent the astro-geodetic measurements without contradiction.
• Possible expansion of the astronomical-geodetic geoid determination with the help of the astronomical- gravimetric leveling (determination of geoid heights or quasigeoid heights through a combination of astro -geodetic and gravity measurements ).
• Geodetic aspects of celestial mechanics
• Determination of the reduction in refraction for terrestrial observational astronomy

The term astronomical geodesy - together with physical geodesy  - also gives its name to numerous university institutes in Central Europe . The name combination of these two subject areas is understood as a counterpart to applied geodesy or the technical tasks of surveying or cadastral practice.

literature

• Karl Ledersteger : Astronomical and Physical Geodesy (Earth Measurement) , JEK Volume V, J. B. Metzler-Verlag, Stuttgart 1968, especially pp. 250-257 and pp. 645-655
• Karl Ramsayer : Geodetic Astronomy , Volume IIa of the manual of surveying JEK , J. B. Metzler-Verlag, Stuttgart 1969
• Kurt Bretterbauer , Harald Schuh : Higher Geodesy . Script for the lecture of the same name, Vienna University of Technology 1998 and 2003
• Albert Schödlbauer: Geodetic Astronomy Basics and Concepts. de Gruyter, Berlin 2000, ISBN 3-11-015148-0

Web links

• Institute for Theoretical Geodesy, University of Bonn
• Institute for Astronomical and Physical Geodesy (IAPG), Technical University of Munich

Individual evidence

1. ↑ Ramsayer, chap. 6, pp. 107-140 and Appendix II, pp. 832 ff.