Towards an Austrian GPS Reference Network

During the past years several activities were launched in Austria to establish a state-of-the- art GPS-network which could serve as a basis for geodynamic applications. Recently, in June 1996, an association of engineering consultants initiated a GPS-campaign which covered the Austrian territory with 330 sites with a mean point-to-point distance of about 25 km. The establishment of such an accurate network (+/- 0.4 cm horizontal, +/- 0.8cm height) will be advantageous to all kinds of surveying activities in the near future and provides a considerable contribution to the densification of the ITRF94 reference frame.The Institute of Theoretical Geodesy and Geophysics (ITGG) in Vienna is one of the two analyses centers, which were appointed to process the GPS-network data. This paper summarizes the computational efforts at ITGG and puts special emphasis on the algorithms used for reference frame fixing in the analyses. Additionally, problems of modelling phase center variations (seven different antenna types were used in the network) are discussed.