DOI: 10.1594/pangaea.921932
title: Multibeam bathymetry processed data (Kongsberg EM 122 entire dataset) of RV MARIA S. MERIAN during cruise MSM57/2

description: Swath sonar bathymetry data used for that dataset was recorded during RV MARIA S. MERIAN cruise MSM57/2 using Kongsberg EM 122 multibeam echosounder. The cruise took place between 13.08.2016 and 07.09.2016 off Svalbard. The cruise investigated gas hydrate systems and their dynamics at the continental margin of Svalbard. The key instrument to be used during this expedition was the Bremen Deep Sea Drill Rig MeBo. Drilling during Leg 2 was concentrated mostly at the uppermost part of the continental slope offshore Prins Karls Forland [DOI: edocx/00105895-1]. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest creation of products and approval.Description of data source:During the MSM57/2 cruise, the hull-mounted Kongsberg EM122 multibeam echosounder (MBES) was utilized to perform bathymetric mapping in middle to deep water depths. Two linear transducer arrays in a Mills Cross configuration transmit acoustic signals of a nominal sonar frequency of 12 kHz. With 432 soundings per swath, the emission cone has a dimension of max 150° across track and 2° along track. With a reception obtained from 288 beams, the actual beam footprint is 2° by 2°. Depending on the roughness of the seafloor, the swath width on a flat bottom is generally maximum six times the water depth. For further information on the system, consult https://www.km.kongsberg.com/. During this cruise the swath width was set to 120° to improve data quality, reduce the amount of noisy data at the outer beams and increase the ping rate. The use of the high-density equidistant and the dual-swath mode of the EM122 resulted in up to 864 soundings per ping. The EM122 was running continuously during the cruise with an average vessel speed of about 4.4 kn. Responsible person during this cruise / PI: C. dos Santos Ferreira (cferreira@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 (Caress, D. W., and D. N. Chayes, MB-System: Mapping the Seafloor, https://www.mbari.org/products/research-software/mb-system, 2017) was utilized for this purpose. A sound velocity correction profile was applied to the MSM57/2 data; while there were no further corrections for roll, pitch and heave applied during postprocessing. A tide correction was applied, based on the Oregon State University (OSU) tidal prediction software (OTPS) that is retrievable through MB-System. CTD measurements during the cruise were sufficient to represent the changes in the sound velocity throughout the study area. Using Mbeditviz, artefacts were cleaned manually. NetCDF (GMT) grids of the edited data as well as statistics were created with mbgrid. The published bathymetric EM122 grid of the cruise MSM57/2 has a resolution of 35 m. No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. 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. The DTMs projections are given in Geographic coordinate system Lat/Lon; Geodetic Datum: WGS84. All grids produced are retrievable through the PANGAEA database (www.pangaea.de).Chief Scientist: G. Bohrmann (gbohrmann@marum.de)A special thanks goes to the watchkeeper during MSM57/2: N. Stange and Michael Riedel