HYDRO 2016 Paper 4B3
Gunter Liebsch, Joachim Schwabe, Wilfried Ellmer, Jonas Ågren, Jyrki Mononen
So far, nautical charts of the Baltic Sea are referenced to a large number of local, tide-gauge based vertical datums. Bathymetric data do not fulfil the requirements of a seamless data set due to the lag of a definition and realisation of an unique height reference frame for the whole Baltic Sea area. Therefore, the Chart Datum Working Group (CDWG) of the Baltic Hydrographic Commission proposed to thoroughly revise the charts based on a common and unified Baltic Sea Chart Datum (BSCD).The new chart datum shall be directly linked to the European Height Reference System (EVRS), which particularly facilitates applications in the coastal areas.
In the future, bathymetric surveys and improved navigation at sea shall be based on refined GNSS techniques also for the vertical component. For this purpose a precise model of the height reference surface – called chart datum in hydrography or geoid in geodesy – is needed. However, the available national and regional models are currently not precise and consistent enough. A unified and precise geoid model requires both unified modelling based on consistent standards as well as shipborne campaigns to collect precise marine gravity data. Therefore, establishing a geoid model which is suitable to realise the BSCD is one major pillar of "FAMOS Activity 2". In that context, "Activity 2" of the FAMOS project, which is co-financed in the frame of the Connecting Europe Facility (CEF) transport program of the European Commission, is concerned with the realisation of a modernised vertical datum in the Baltic Sea. Goals of "FAMOS Activity 2" are the collection of new gravity data over the Baltic Sea, the stimulation of a mutual data exchange, the validation of existing data and the computation of a geoid model with an accuracy of at least 5 cm by 2020. The presentation describes the background and current developments for the realisation of the Baltic Sea Chart Datum 2000 (BSCD2000) in the frame of "FAMOS Activity 2". Special emphasis is put on the activities in the southern Baltic Sea.