Germany (GCG2011-NORTH)
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Authors: A. Rülke, et al.
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Created: 2011
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Resp: BKG
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Description:
The German Combined QuasiGeoid GCG2011 is a high-resolution hybrid model for Germany computed by the "Bundesamt für Kartographie und Geodäsie" (BKG) and the
"Institut für Erdmessung" (IfE). The final solution was computed as the average of the two individual solutions from BKG and IfE. The GCG2011 model
allows a direct transformation between ellipsoidal heights in the terrestrial reference system ETRS89 (SAPOS realization) and physical heights in the
system DHHN92 (normal heights).
The computation procedures at BKG and IfE are both based on the remove-restore technique. The input data are high-resolution gravity and terrain data, a
global geopotential model, as well as GPS and levelling control points. The gravity stations (approx. 400,000) have a spacing of a few km, while the existing
digital terrain model has a grid spacing of 1"x1" (corresponds to about 30 m block size). The BKG quasigeoid modelling is based on the adjustment of point
masses that are located in grids at different depths. In a common adjustment of gravity and GPS/levelling data, the point masses are adjusted for given
locations. The masses are then used for the derivation of quasigeoid undulations at any location. The quasigeoid modelling at IfE is based on integration
and collocation techniques that are applied in a two-step procedure. In the first step, the gravity and terrain data are combined with the global geopotential
model by spectral combination with integral formulas. This gravimetric solution is then combined in a second step with GPS and levelling data by collocation
techniques. Contrary to the previous solution of IfE in 2003 (based on the EGG97 gravimetric geoid), this time a complete re-processing of all gravity and
terrain data was done for the combination with GPS and levelling control points.
The accuracy of the final GCG2011 was estimated as about 1-2 cm using partial solutions and independent GPS and levelling data. The model is
available for users at the BKG geodata center.
References:
G. Liebsch, U. Schirmer, J. Ihde, H. Denker, J. Müller (2006). Quasigeoidbestimmung für Deutschland.
Deutscher Verein für Vermessungswesen - Schriftenreihe, 49, pp. 127-146.
A. Rülke, G. Liebsch, U. Schäfer, U. Schirmer, J. Ihde (2012). Geoid determination in Central Europe
based on terrestrial data and GOCE observations. EGU General Assembly, 22-27 April 2012, Vienna, Austria.
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