[G02-5] Altimetry and marine geoid

[G02-5-03] Overview of the FAMOS efforts to improve the Baltic Sea geoid model by new marine gravity measurements

^○Jonas Agren¹, Joachim Schwabe², Gabriel Strykowski³, Rene Forsberg³, Gunter Liebsch², Christoph Foerste⁴, Franz Barthelmes⁴, Mirjam Bilker-Koivula⁵, Artu Ellmann⁶, Silja Maerdla⁶ (1.Lantmateriet, the Swedish mapping, cadastral and land registration authority, Gavle, Sweden, 2.Bundesamt fur Kartographie und Geodasie, Leipzig, Germany, 3.Technical University of Denmark, National Space Institute, Copenhagen, Denmark, 4.GFZ German Research Centre for Geosciences, Potsdam, Germany, 5.Finnish Geospatial Research Institute, National Land Survey of Finland, Masala, Finland, 6.Tallinn University of Technology, School of Engineering, Tallinn, Estonia)

The Baltic Sea Hydrographic Commission (BSHC) has decided to introduce the Baltic Sea Chart Datum 2000 as new common reference system for the Baltic Sea nautical charts from 2020. The Baltic Sea Chart Datum 2000 is a geodetic height reference system that uses an equipotential surface as zero level. It is based on the definition of the European Vertical Reference System (EVRS) as well as on the European Terrestrial Reference System 89 (ETRS89). The reference epoch for the postglacial land uplift is 2000.0. On land, the Baltic Sea Chart Datum 2000 will – for the time being – primarily be realized by the national levelling height reference frames. Offshore, it will be realized by GNSS (relative to networks of permanent reference stations) and a height reference surface constructed based on a gravimetric geoid model.

One of the key tasks of activity 2 in the FAMOS (Finalizing Surveys for the Baltic Motorways of the Sea) project is to improve the gravimetric geoid model over the Baltic Sea, aiming at the above realization. It is required that the model is ready by 2020 and has a well corroborated standard uncertainty better than 5 cm. This will be reached mainly (but not only) by validating and complementing the existing gravity data, with new marine gravimetry measurements made from the FAMOS hydrographic surveying vessels. Up to 2016, eight marine gravimetry campaigns have been finalized, and new FAMOS gravity and GNSS/levelling databases have been set up. It is the intention in the project to compute many interim geoid models using different computation methods on a successively improving gravity dataset. The purpose of this contribution is to give an overview of the marine gravimetry campaigns performed, present the status of the FAMOS databases and shortly describe the computation of the first FAMOS preliminary interim geoid models.