On Modelling the Regional Distortions of the European Gravimetric Geoid EGG97 in Romania

We analyze and model the regional distortions of the European Gravimetric Geoid 1997 (EGG97) in Romania using GPS-levelling data. A comparison of the EGG97 gravimetric quasi-geoid with the GPS-levelling data indicates the presence of significant regional distortions in particular areas along the border of the country. To model the regional distortions, we apply two methods: (i) the recently proposed innovation function approach by Prutkin and Klees (J. Geod. 82(3), 147–156, 2007), which is based on a mathematical formulation of the differences between gravimetric quasi-geoid and GPS-levelling data in terms of a Cauchy boundary-value problem for the Laplace equation. (ii) the conventional approach of a low-degree polynomial correction surface. The results reveal that the innovation function approach gives more options to model a more complex trend of the regional gravimetric quasi-geoid distortions than the correction surface approach.