Comparison of geoid models over Fennoscandia

摘要

To get inside into the latest geoid models that were obtained with the data from the CHAMP satellite, different geoid models are compared with each other and with ground data. Seven geoid models are considered: The global models OSU91A and EGM96, the European model EGG97, the Nordic model NKG96, the newest model for Finland FIN2000, and the two global models that include CHAMP data: TEG-4 and the satellite only model EIGEN-1S. For ground truth, a total of 245 points in Finland and Sweden are available. For all points, GPS-determined heights are available as well as orthometric or normal heights based on spirit levelling. Geoid heights obtained from these heights are compared with the values obtained from the geoid models. Corrections are applied to the height differences for the land uplift and a bias and tilt are removed to adjust to the national height systems. When comparing with the ground truth, unmodelled long-period signals show up in the differences with OSU91A, EGM96, EGG97 and NKG96. Comparison of TEG-4 and EIGEN-1S grids with an EGM grid show a change in geoid height up to 0.5 meter in the centre of the Baltic Sea.