GEOnAUT - The Austrian Geoid 2007

A new Austrian geoid model has been computed as a combined solution of local terrestrial gravity field observations (gravity anomalies, deflections of the vertical, "direct" geoid observations obtained by a difference between geometric heights derived from GPS observations, and orthometric heights derived from spirit levelling), and global gravity field information based on data of the satellite gravity mission GRACE.

Short Description

The terrestrial data are mainly sensitive to medium to high wavelengths. The incorporation of the global gravity field model, representing the long-wavelength information, results in a stabilization of the solution and a reduction of systematic effects such as biases and tilts.

The data bases of gravity anomalies, deflections of the vertical, and GPS/levelling information have been thoroughly validated, and new measurements of deflections of the vertical in the South- East of Austria have been performed. Additionally, a new digital terrain model (DTM) has been assembled as a combination of highly accurate regional DTMs of Austria and Switzerland, complemented by data of the Shuttle Radar Topography Mission (SRTM) in the neighbouring countries.

In addition to methodological developments of the standard technique of Least Squares Collocation (LSC), several alternative methods for the optimum combination of different (global and local) data types, such as tailored series expansion (based on spherical harmonic base functions), multi-resolution analysis using spherical wavelets, fast multipoles techniques, and algebraic approximation methods have been investigated. For the final geoid solution, the LSC technique, representing the most mature approach, has been applied.

The new Austian geoid solution, complemented by covariance information, has been thoroughly validated. The accuracy of this new solution can be estimated to be of the order of 2 to 3 cm. Thus, compared to the previous official Austrian geoid model, the accuracy and reliability was significantly improved. This is mainly due to the substantially improved quality of the input data, as well as several methodological developments performed in the frame of this project.

Project Partners


Graz University of Technology, Institute of Navigation and Satellite Geodesy - Roland Pail


  • Graz University of Technology, Institute of Computational Mathematics - Olaf Steinbach
  • Federal Office of Metrology and Surveying - Norbert Höggerl

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