Geodetic astronomy


Geodetic astronomy or astronomical geodesy is the application of astronomical methods into geodetic networks and other technical projects of geodesy.

Applications

The most important applications are:
Important measuring techniques are:
The accuracy of these methods depends on the instrument and its spectral wavelength, the measuring or scanning method, the time amount, the atmospheric situation, the stability of the surface resp. the satellite, on mechanical and temperature effects to the instrument, on the experience and skill of the observer, and on the accuracy of the physical-mathematical models. Changing weather or atmospheric conditions near the observation site can negatively affect atmospheric refraction in the zenithal direction, referred to as anomalous or zenithal refraction; anomalous refraction is considered to be the primary source of error in geodetic astronomy deflection data.
Therefore, the accuracy reaches from 60" to 0,001" and better, e.g.:
  • angles ±1" up to 0,1"
  • geoid determination & height systems ca. 5 cm up to 0,2 cm
  • astronomical lat/long and star positions ±1" up to 0,01"
  • HIPPARCOS star positions ±0,001"
  • VLBI quasar positions and Earth's rotation poles 0,001 to 0,0001"
Astrogeodetic leveling is a local geoid determination method based on vertical deflection measurements. Given a starting value at one point, determining the geoid undulations for an area becomes a matter for simple integration of vertical deflection, as it represents the horizontal spatial gradient of the geoid undulation.