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Regional Models

Switzerland and Liechtenstein (CHGeo2004)

  Author: U. Marti     Created: 2004    Resp: U. Marti  
      Status: PUBLIC    
The CHGeo2004 geoid and quasigeoid model of Switzerland was computed by Federal Office of Topography (Swisstopo) and it is the official geoid model to be used in Switzerland and Liechtenstein. It covers the area from 45° 45' N to 47° 51' N in latitude and from 5° 51' E to 10° 30' E in longitude with a grid resolution of 30". It is referred to the GRS80 normal ellipsoid in the ETRS89/CHTRF95 frame. It is a hybrid model because it was computed by combining astrogeodetic data (about 700 deflections of the vertical), gravimetric data (about 40000 gravity measurements) and GPS/levelling data (about 200 stations). All the available gravimetric data were reprocessed to bring them to a common datum, to eliminate gross errors and to produce a grid with a resolution of 5 km. In the framework of a remove-compute-restore procedure, the observations were reduced by contribution of the EGM96 global geopotential model up to degree and order 360, as well as the DHM25 national digital terrain model with 25 meter resolution and SRTM3 outside its domain. A further reduction was computed by considering a density model of the Earth’s crust, including a Moho model, a model of the Ivrea body, sediments of rivers, water masses of lakes and the ice thickness of large glaciers. Since the effect of these crustal models was partly included into the global model, only the remaining effect was used for the data reduction. From the residual gravity field, the geoid as well as the quasi-geoid were obtained by least squares collocation, with a strong weight on GPS/levelling data so that these observations got practically no residuals. The obtained solutions have an accuracy of the order of 2-3 cm as could be verified by comparison with independent data. The CHGeo2004 geoid and the CHQua2004_RPN quasi-geoid models are compatible with the LHN95 Swiss heigh datum, whereas the CHQua2004_EF quasi-geoid model is compatible with the EVRF2000 height datum and it is just a shifted version of CHQua04_RPN by 10.31 cm. Another variant is the CHGeo2004_htrans height transformation surface which is compatible with the LN02 official Swiss heights.

U. Marti (2004). High Precision combined geoid determination in Switzerland. Proc. of the IAG GGSM2004 Symposium, Porto, Portugal.
U. Marti (2007). The National Geoid Model CHGeo2004. In: M. Troller, A. Wiget, U. Marti, H.-G. Kahle, P.-Y. Gilliéron (eds), Swiss National Report on the Geodetic Activities in the Years 2003-2007, pp. 52-55, Swiss Geodetic Commission.
U. Marti (2007). Comparison of high precision geoid models in Switzerland. In: P. Tregonig, C. Rizos (eds), Dynamic Planet: Monitoring and Understanding a Dynamic Planet with Geodetic and Oceanographic Tools, IAG Symposia Series, vol. 130, pp. 377-382, Springer Verlag.

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