Terms of Reference and Objectives

The primary objective of the project is the development of an improved geoid and quasigeoid model for Europe. The previous European Gravimetric Geoid 1997 (EGG97) is based on high-resolution gravity and terrain data and the global model EGM96. The comparison of the EGG97 model with GPS/leveling data from national campaigns and the continental-scale EUVN project reveals long wavelength discrepancies (at the dm level), while the agreement at shorter wavelengths is at the cm level in many cases. For GPS heighting such long wavelength geoid errors are vital and have to be modeled, e.g., by fitting the geoid model to some GPS/leveling control stations.

Since the development of the EGG97 model, several new data sets and computing techniques have become available. Hence, significant improvements (especially at the long wavelengths) can be expected from an updated European geoid model. Besides the new modeling techniques (e.g., wavelets), improvements are expected from the new CHAMP and GRACE global geopotential models, new terrain data sets (e.g., GTOPO30, SRTM results, national data sets), new and more homogeneous gravity data sets for some regions, new altimetric results, an improved merging of ship and altimetric gravity data, and the use of continental-scale GPS/leveling campaigns. The data collection effort will focus especially on the problem areas in the EGG97 computation, i.e., areas where gravity field data is lacking, sparse, or of low quality.

All relevant work within the project requires close international cooperation between all European countries and different IAG bodies. The contacts and successful cooperation with the respective national and international agencies, established within the framework of the EGG97 model development, will be continued and extended. The project is open to all agencies and universities with an interest in the development of a geoid and quasigeoid model for Europe.

The objectives of the project are summarized below:
- Collection, evaluation and homogenization of land and marine gravity data, altimetric data, GPS/leveling data, digital elevation models, and global geopotential models.
- Creation of databases for different data types.
- Investigation of different techniques for regional geoid and quasigeoid determination.
- Investigation of techniques for the combination of gravimetric and GPS/leveling data.
- Development of a new European geoid and quasigeoid model (gravimetric and/or combined model).