EUREF, the IAG (International Association of Geodesy) Reference Frame Sub-Commission for Europe, is responsible for the definition, realization, and maintenance of the European Reference Frame ETRS89 (European Terrestrial Reference System). The European Permanent Network (EPN) plays a key role in these activities. It comprises about 192 (as of 2006, October 1st permanent tracking stations, continuously observing the GPS and (at least some receivers) GLONASS constellation.
Data of these tracking sites is processed by currently 16 Analysis Centers following a distributed data processing approach. The individual subnetwork results are combined to a final EUREF SINEX (Software INdependent EXchange format) solution based on the full covariance information of the single contributions. This task is carried out by the EPN Combination Center which is located at the Bundesamt für Kartographie und Geodäsie (BKG, Frankfurt a. M., Germany). The combined SINEX solution is sent to the IGS (International GNSS Service) every week for inclusion into the IGS densified network solution.
CODE is one of the EUREF Analysis Centers and processes a EPN subnetwork of about 50 stations on a daily basis. A weekly coordinate solution is computed and submitted to the EUREF. In addition, daily troposphere parameter estimates (zenith path delays) for all stations are delivered.
Such a regional network is an ideal test environment for different processing strategies. Always striving to heighten the understanding of GNSS data processing and getting the best out of available data, eight additional solutions are computed besides the official one.
These test solutions are used to try out refined processing options such as inclusion of low-elevation data and estimation of tropospheric gradient parameters, but also to compare different orbit products from IGS and CODE.
CODE computes all results with the in-house developed Bernese GPS Software, a high-performance software package for scientific GNSS data processing. It is worth mentioning that 13 of the other 15 Analysis Centers use the Bernese GPS Software package to compute their individual EUREF contributions, too.