DOI: 10.1594/pangaea.919772
title: Multibeam bathymetry processed data (EM 120 echosounder entire dataset) of RV METEOR during cruise M79/2

description: Swath sonar bathymetry data used for that dataset was recorded during RV METEOR cruise M79/2 using Kongsberg EM 120 multibeam echosounder. The cruise took place between 26.08.2009 and 21.09.2009 in the northeastern Atlantic. The main objectives of the cruise were the analysis of the structure, dynamic and natural hazard potential of the Atlantic section of the European-African plate boundary in the area of the eastern Azores (São Miguel region) and Gloria Fault. The measurements included marine geophysical experiments like refraction and reflection seismics, potential field recordings (gravity & magnetics), parametric sediment subbottom profiling and multibeam bathymetry [DOI:10.2312/cr_m79_2].CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest and approval.Description of the data source:During the M79/2 cruise, the hull-mounted KONGSBERG EM120 multibeam ecosounder (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 191 beams, the emission cone has a dimension of max. 140° across track and 1° along track. With a reception obtained from 288 beams, the actual beam footprint is 1° 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/. Responsible person during this cruise / PI: Luis Batista.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. . SVPs taken during this cruise were not sufficient enough to correct the recorded bathymetric data. Therefor sound velocity profiles were modelled using reference profiles from the world ocean atlas (S. Levitus, 1982),extracted and calculated through the MB-System program mblevitus byutilizing the DelGrosso equation. The surface sound speed has then been adapted according to the recordings during this cruise 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 EM120 grid of the cruise M79/2 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: Christian Hübscher christian.huebscher@uni-hamburg.deCR: https://www.tib.eu/de/suchen/id/awi%3Adoi~10.2312%252Fcr_m79_2/CSR: https://epic.awi.de/id/eprint/37063/31/m79-expeditionsheft.pdf