GEODESEA-2019 An experiment of seafloor geodesy in the Bay of Brest

In the framework of the ERC FOCUS project, the Geosciences Ocean Laboratory (LGO) organized, from July 22 to 26, 2019, an experiment of seafloor geodesy in the Bay of Brest, entitled Geodesea-2019. The aim was to test acoustic beacons acquired for the FOCUS project and to test experimental protocols for seafloor positioning. The experiment was carried out from the Albert Lucas research station-vessel. The experiment was conducted in collaboration with the Laboratoire Environnement et Sociétés (LIENSs) from la Rochelle and the iXBlue company, in Brest. Relative acoustic ranging was carried out during four days, each beacon ranging the other ones at a regular time interval, while acquiring auxiliary data (temperature, pressure, sound-speed) to be able to convert travel-times into distances. Absolute positioning of the beacons on the seafloor was also carried out using a small Unmanned Surface Vehicle (USV) on which a compact GNSS/Acoustic system was mounted, combining an Ultra Short Baseline (USBL), an inertial system (INS) and a GNSS receiver.