Gridded ELAC SB3050 multibeam-echosounder bathymetry of cruise POS498

Bathymetry based on data recorded during POS498 between 18.04.2016 and 01.05.2016. The cruise aimed to recover observatories with the help of the Remotely Operated Vehicle (ROV) MARUM‐SQUID, while the second main objective of the cruise was to recover sediments to study the thermal structure as well as the temporal evolution of the mud volcanoes. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry post-processing and its products. Description of the data source: During the RV POSEIDON cruise POS498 the ELAC SB3050 multibeam echo sounder with a nominal sounding frequency of 50 kHz was utilized. 384 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.mdsys.co.kr/down/ELAC/SB_3050.pdf. During POS498 the swath angle was set mostly between 90 and 70° with a survey speed of 6 knots. The ELAC SB3050 worked reliable. Problems during the acquisition were during bad weather conditions and a malfunction of the integrated navigation system (F180 unit) by which the heading of the ship in the data diverged from the true heading, which resulted in misplaced beams. Responsible person for hydroacoustics during this cruise / PI: David Voelker (dvoelker@marum.de). Description of data processing: Postprocessing and products were conducted by the Seafloor-Imaging & Mapping group of MARUM/FB5, responsible person: Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-System suite (Caress, D.W., and D.N. Chayes, MB-System Version 5.5, 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. Though CTD measurements were taken during the POS498 cruise, and these were most of the time sufficient to represent the changes in the sound velocity (SVP) throughout the study area, some SVP's had to be reanalysed. Changes in SVP were applied (mbset) while further roll, pitch and heave corrections were not necessary for the POS498 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 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 70 m. A higher resolution is, at least partly, achievable. The grid extended with _num represents a raster dataset with the statistical number of beams/depths taken into account to create the depth of the cell. The extended _sd -grid contains the standard deviation for each cell. All grids produced are retrievable through the PANGAEA database (www.pangaea.de). Chief Scientist: H. Sahling (hsahling@marum.de) CR: http://oceanrep.geomar.de/33307/ CSR: http://www.bsh.de/aktdat/dod/fahrtergebnis/2016/20160082.htm A special thanks goes to the watch keeper of the hydroacoustic systems during POS498: David Volker, Markus Loher Another thanks goes to the student helper, that helped to create the product: Stefanie Gaid