Investigation of different methods for the combination of gravity and GPS/levelling data
Two different methods for the combined computation of the quasigeoid are compared in a test area in Germany. Both methods are based on the remove-restore technique and use the global geopotential model EGM96, point gravity data with a spacing of a few km, a digital terrain model and GPS/levelling control points (with a spacing of about 25 km).
In method I the global model is combined first with the gravity and terrain data using the least squares spectral combination technique with integral formulas. The resulting height anomalies are given in a 1.0 ’x 1.5’grid. Then a smooth corrector surface is developed from the GPS/levelling data by least squares collocation, using a signal and a trend component.
The second method (II) is based on a common adjustment of the EGM96 reduced gravity and height anomaly observations using point masses and appropriate weight relations. The point masses are arranged at a depth of 10 km, 30 km and 200 km, and in hilly areas also at a depth of 5 km.
Both techniques are compared from the methodological and numerical point of view. The results are discussed and show an agreement at the cm level.
KeywordsGeoid levelling gravity GPS
Unable to display preview. Download preview PDF.
- Denker, H. (1998): Evaluation and improvement of the EGG97 quasigeoid model for Europe by GPS and levelling data. Second Cont. Workshop on the Geoid in Europe, Rep. Finn. Geod. Inst. 98:4, 53–61, Masala, 1998.Google Scholar
- Denker, H., W. Torge (1997): The European gravimetric quasigeoid EGG97 — An IAG supported continental enterprise. In: R. Forsberg et a1. (eds.): Geodesy on the Move, IAG Symp., Vol. 119, 245–254, Springer, Berlin, Heidelberg, New York, 1998.Google Scholar
- Ihde, J. (1995): Geoid Determination by GPS and Levelling. In: International Association of Geodesy. Symposia 113, Gravity and Geoid. Springer-Verlag Berlin, HeidelbergGoogle Scholar
- Ihde, d., Schirmer, U., Stefani, F:, T6ppe, F. (1998): Geoid Modelling with Point Masses. In: Proceedings of the Second Continental Workshop on the Geoid in Europe, Reports of the Finnish Geodetic Institute. Budapest, Hungary, March 10–14, 1998Google Scholar
- Lemoine, F. G. et a1. (1996): The Development of the NASA GSFC and NIMA Joint Geopotential Model. In: Proceedings of the International Symposium on Gravity, Geoid, and Marine Geodesy, (GRAGEOMAR1996). The University of Tokyo, Tokyo, Japan, September 30 – October 5, 1996Google Scholar
- Milbert, DG . (1995): Improvement of a high resolution geoid height model in the United States by GPS height on NAVD 88 benchmarks. Bull. d’Informations 7? and IGeS Bull. 4, Special Issue, New Geoids in the World, 13–16, Milan, Toulouse.Google Scholar