Bathymetry based on data recorded during POS317-4 between 16.10.2004 and 04.11.2004. This cruise focused on methane seeps off Georgia and Turkey. Different geological settings were studied by using pressurized sampling techniques and remotely operated vehicles (ROVs).

Detailed description:During the cruise POS317-4 the ELAC BottomChart MkII system, consisting of 50 kHz transducers/receivers which were mounted in the moon pool of the ship. The ELAC MkII uses a nominal sounding frequency of 50 kHz. 129 beams are formed for each ping while the seafloor is detected using amplitude and phase information for each beam sounding. For further information, consult http://www.ssrsurvey.com/ssrELACMultibeam.pdf. During POS317-4, while generally surveying in water depths greater than 1000 m, an opening swath-angle of 80 degrees was chosen, with a survey speed of 6 knots. The sea was very calm most of the time during surveying. Responsible person for hydroacoustics within this cruise / PI: Dietmar Bürk (Former employee of GEOMAR & Helmholtz-Zentrum-Geesthacht), Heiko Sahling (hsahling@marum.de) Description of data processing:Postprocessing and products were conducted by the Seafloor-Imaging group of MARUM, responsible person: Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-system (Caress, D.W., and D.N. Chayes, MB-System Version 5, Open source software distributed from the MBARI and L-DEO web sites, 2000-2012.) was utilized for this purpose. A tide correction was applied, based on the Oregon State University (OSU) tidal prediction software (OTPS) that is retrievable through MB-System. In general, there is a tide differences of less than 20 cm in the Black Sea. Further lever-arm or offsets for roll, pitch, heave, heading or sound velocity corrections were not applied to the POS317-4 data. Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. NetCDF (GMT) grids of the product and the statistics were created using mbgrid. Quality assurance was furthermore proven by visual and statistical comparison of crossing survey-lines from different cruises throughout the Black Sea. No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. The currently published bathymetric grid of the cruise has a resolution of 125 m. A higher resolution is, at least partly, achievable.