Finalising Surveys for the Baltic Motorways of the Sea (FAMOS): GFZ

Finalising Surveys for the Baltic Motorways of the Sea (FAMOS)

The photo shows the Finnish survey ship "Airisto" about 100 meters away from the viewer in the harbor basin of the Finnish town of Mäntyluoto. It has just cast off and is about to leave the harbor. The ship is facing the viewer with its port side. It is about 30 meters long and has the inscription "SURVEY" written on its side in capital letters. Above the bridge is the inscription www.meritaito.fi. This is the website of the shipping company of this ship. — 2015-Airisto *(Photo: Ch. Förste, GFZ)*

This photo shows the German survey ship "Deneb" in the harbor of the Danish town of Bornholm. The viewer looks diagonally from the front at the bow and port side of the ship from the harbor basin. The ship is about 100 meters away from the viewer. It is moored along its starboard side to the harbor wall and you can see the church of Bornholm and houses next to it about 1 kilometer away in the background. There is a lighthouse between the houses. The ship is about 52 meters long, 11 meters wide and more than 20 meters high with the mast. It has the inscription "DENEB" on the bow. — 2015-Deneb *(Photo: Ch. Förste, GFZ)*

This photo shows the Swedish survey ship "Jacob Hägg" in a harbor near Gävle. It is about 36 meters long and 7.5 meters wide and 15 meters high with the mast. The ship is about 50 meters away from the viewer. The viewer looks diagonally from the edge of the harbor basin at the bow and starboard side of the ship. The ship is moored along its port side to the harbor wall. On the bow and on the side of the bridge it bears the inscription "JACOB HÄGG". The coat of arms of the Swedish Maritime Administration with an anchor and royal crown is attached to the chimney. In the background you can see the forests of the coastal region. — 2016-Jacob Hägg *(Photo: Ch. Förste, GFZ)*

GFZ/Section 1.2 was cooperation partner of the EU project FAMOS (Finalising Surveys for the Baltic Motorways of the Sea). Among others, FAMOS included all aspects of hydrographic surveying in the Baltic Sea according to the recommendations of the Baltic Sea Hydrographic Commission (HSHC) and the Baltic Marine Environment Protection Commission (Helsinki Commission – HELCOM).

FAMOS was a joint project of hydrographic, maritime and geodetic institutions and agencies of almost all EU countries around the Baltic Sea. FAMOS was co-funded by the European Commission within the Connecting Europe Facility (CEF Transport). FAMOS aimeds to improve the safety on the motorways of the sea in the Baltics. Part of the FAMOS activities was estimation of a new gravimetric geoid as common and unified chart datum in this sea.

- Project management: Swedish Maritime Administration (Sjöfartsverket)

- Geodetic project partners:

Deutsches GeoForschungsZentrum GFZ, Bundesamt für Seeschiffahrt und Hydrographie, Federal Agency for Cartography and Geodesy (BKG)
Technical University of Denmark (DTU Space)
Lantmäteriet (Schweden)
National Land Survey of Finnland (NLS)

The FAMOS project started in 2014 und was finalized by 2019. The geoid determination in the FAMOS project was co-funded by the EU Commission with 50% of the costs. The calculation of the new gravimetric geoid (the Baltic Sea Chart Datum 2000) is currently being completed under the direction of the HSHS Chart Datum Working Group.

GFZ’s contribution in the FAMOS project was conduction of shipborne gravimetry campaigns including the related data processing. The shipborne gravity measurements for FAMOS were done with the Chekan-AM gravimeter equipment.

This illustration shows the results of the evaluation of gravity measurements on the Finnish survey vessel "Airisto" in the Bothnian Sea in autumn 2015. The figure consists of three individual images or plots. Top right is a photo of a scientist standing in front of the "Airisto" moored to a harbor wall. He is holding a remote control with which he operates a gravimeter on the ground in front of him. The Finnish flag is flying at the stern of the ship. Below this photo is a map of the Bothnian Sea, showing the lines surveyed by "Airisto" in this part of the Baltic Sea. One of these lines is marked. On the left-hand side of the illustration, the gravity variations obtained along this line are shown in a plot as a function of measurement time. It is a gravity curve that runs over about 14 hours, starting at about -60 mGal, rising to a maximum value of about 20 mGal after 5 hours and then falling to about -20 mGal towards the end of the time series. For comparison, the values of a global gravity field model (EIGEN-6C4) are drawn as a second curve behind it. This gravity field model was calculated from satellite data and earlier terrestrial gravity measurements. It shows a high degree of agreement with the gravity data measured on "Airisto". A third curve drawn below shows the variations in the water depth under the track driven. It varies between about -80 and -100 meters. — Data processing results for gravity measurements collected onboard the Finnish survey vessel MSV “Airisto“ in autumn 2015 on Bothnian Sea: The plot on the left hand side gives gravity variations based on Chekan-AM measurements (blue) along the red marked track (right). Values of the gravity field model EIGEN-6C4 are given for comparison (green). This global model is based on satellite and terrestrial data. Furthermore, bathymetry is given on the plot left (brown) *(Ch. Förste, GFZ)*

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