Assessment of the Greek Vertical Datum – A case study in central Greece
21/09/2016 | 17:00 | Session 5: Height systems and vertical datum unification
Author(s): Vassilios Grigoriadis, Evangelia Lambrou, Georgios Vergos and Ilias Tziavos
Vassilios Grigoriadis, Evangelia Lambrou, Georgios Vergos and Ilias Tziavos
A consistent and unified National Vertical Datum is of main importance for a wide range of applications in geosciences and engineering projects, the latter including infrastructure development, public works and monitoring of natural risks and disasters. The inherent inconsistencies and shortcomings of the Greek Vertical Datum (GVD), mainly due to a) the lack of connection between the VD of the islands with that of mainland Greece, b) the lack of a unified adjustment of the old trigonometric network and c) the lack of any practical long term monitoring of the VD variation with time, pose a problem that needs to be tackled in support of engineering and other studies. In the present study the consistency of the GVD is examined, focusing on an area in central Greece and following similar efforts already made in previous researches for the establishment of an International Height Reference System (IHRS). High precision GNSS measurements are available at trigonometric benchmarks located along the Gulf of Corinth, with benchmarks residing on both coasts along. First, the zero-level geopotential value (Wo) for the two areas, north and south coast, has been determined, based on the classical Helmert theory using GNSS/leveling data and surface geopotential values derived from GOCE-based global geopotential models (GO-DIR-R5, GO-TIM-R5, GOCO05s and GECO) and EGM08. Then, the relative offset between the two areas has been estimated and compared with previous results on the GVD and the VD of the Greek islands. Furthermore, the local Wo estimations were compared with the corresponding adopted value for the IHRS. Finally, some remarks were drawn on the feasibility of the unification of the GVD with a global one.