GCG2016 – the new height reference surface for Germany
21/09/2016 | 14:30 | Session 3: Regional and Local Geoid Modelling
Author(s): Joachim Schwabe, Gunter Liebsch and Uwe Schirmer
Joachim Schwabe, Gunter Liebsch and Uwe Schirmer
In 2016, a fully modernized height reference will be implemented in Germany. This includes all three quantities involved in GNSS leveling, i.e., ellipsoidal heights from GNSS, normal heights, and a consistent quasigeoid model. The presentation thus highlights the following developments:
The leveling network of the first order has been fully re-measured and adjusted, resulting in the new reference frame DHHN2016.
A complete set of GNSS-based ellipsoidal heights was also observed throughout Germany and adjusted with respect to the same common epoch. These GNSS data were also used to define a new national realization of ETRF2000 called DREF91(R2016).
The German Combined Quasigeoid (GCG) is then the official transformation model between ellipsoidal heights from GNSS and the leveling heights. The new model GCG2016, which is also to be released and adopted in late 2016, is based on a considerable amount of new gravity data over Germany. These cover, for example, the marine near-coastal regions, the mudflat areas of the North Sea, and Lake Constance. Further improvements of the quasigeoid model include, among others, application of an updated pointmass method and a refined residual terrain modeling.
Finally, the increased quality of the height reference in Germany is demonstrated through comparison with previous realizations. This unique and homogeneous set of geodetic data is expected to allow consistent GNSS-based height determination in Germany at the centimeter level. The agreement with the national quasigeoid models of neighboring countries is also discussed.
In our view, such comparisons of the national geoid solutions could be useful for the unification of height systems within Europe. They could also stimulate the collaboration between neighboring countries regarding their respective national geoid solutions, in particular regarding the exchange of data. The FAMOS project, aiming at establishing a new geoid-based nautical chart datum for the Baltic Sea, is exemplarily mentioned.