Bathymetric data based on the multibeam echosounders (MBES) KONGSBERG EM120 and EM1002 was conducted during R/V MARIA S. MERIAN cruise MSM16/3 between 13.10.2010 and 20.11.2010 in the Eastern Atlantic off Mauritania. The expedition aimed at a comprehensive understanding of the complex sedimentary system on the Mauritian Shelf as an atypical tropical eutrophic ecosystem and an archive of palaeoclimatic change in Africa during the Holocene. During the expedition, the chain of Mauritian coral reef mounds was mapped for the first time, carbonate-producing organisms successfully sampled and the flooding history of the Golfe d'Arguin investigated. Hydroacoustic surveys were conducted for a better understanding of the topography, and particularly for the identification of coral mounds and their morphological and structural patterns. In addition to bathymetric mapping, further instruments complemented the research programme, such as the sub-bottom profiler PARASOUND, a fast-rescue boat for shallow water surveys, various sediment sampling and coring devices, a CTD, an aerial dust collector and a remotely operated vehicle (ROV).
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 MSM16/3 expedition, the hull-mounted KONGSBERG EM120 multibeam ecosounder (MBES) was utilized for bathymetric mapping in water depth beyond 800 m as it allows accurate bathymetric mapping up to full ocean depth. Two linear transducer arrays in Mills Cross configuration transmit a nominal sonar frequency of 12 kHz with an emission beam of 150° across track and 1° along track, and receive 191 beams with widths of 2° across track and 20° along track. The actual footprint of a beam has a dimension of 1° by 2°. On flat bottom, the achievable swath width can reach up to six times the water depth. The angular coverage sector and beam pointing angles were set to vary automatically with depth according to achievable coverage. For further information on the system, consult https://www.km.kongsberg.com/.
The depth of the water column is estimated through the two-way-travel time, beam angle and ray bending due to refraction in the water column by sound speed variations. Combining amplitude (for central beams) and phase (for slant beams) provides accuracy practically independent of the beam-pointing angle.
Responsible persons during this cruise / PI: Andre Freiwald (andre.freiwald@senckenberg.de), Till Hanebuth (thanebuth@coastal.edu) & Stephen Schilling
Chief Scientist: Hildegard Westphal (hildegard.westphal@zmt-bremen.de)
CR: https://www.tib.eu/en/search/id/awi%3Adoi~10.2312%252Fcr_msm16_3/
CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2010/20100362.htm
Between 12.11.2003 and 30.12.2003, bathymetric data was acquired in the Gulf of Cadiz during the R/V SONNE cruise SO175. The expedition aimed at a better understanding of the interaction between dynamic processes in a seismically active region with slow plate convergence. In the context of earthquake nucleation and subduction zone processes, the multidisciplinary research programme focused on physical and chemical behavior of sediments, pore water and fluids, exploration of the temperature field of the 1755 thrust earthquake event, the quantification of microbial activity, faunal assemblages, gas hydrates and the deployment of a long-term pressure probe. Bathymetric mapping with the multibeam echosounder (MBES) SIMRAD EM120 was utilized to image the nature of the Gibraltar Arc thrust wedge, a proposed subduction zone, and identify possible sampling sites. Sub-bottom profiling, seismic reflection imaging, heat flow measurements, the deployment of an Ocean Floor pore pressure system as well as video-guided systems and coring complemented the research programme.
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 SO175 cruise, the hull-mounted multibeam echosounder (MBES) SIMRAD EM120 was utilized to perform bathymetric mapping. It allows to conduct surveys in water depths of up to 11,000 m. Two transducer arrays transmit frequency coded acoustic signals (11.25 to 12.6 kHz). Data acquisition is based on successive emission-reception cycles of the signal. While the emission beam has a dimension of 150° across and 2° along track, the reception is obtained from 191 overlapping beams with widths of 2° across and 20° along track. The beam footprint has a dimension of 2° by 2°. The beam spacing can be set to equidistant or equiangular. For further information on the system, consult: https://www.km.kongsberg.com/
During the cruise, an opening angle of 60-70° was used depending on the state of the sea, restricting the coverage to a maximum 14 km wide swath to gain a more continuous spacing of beams on the ocean floor. The spacing within these limits was controlled automatically by the echosounder system.
To convert the recorded travel times into water depth, several sound velocity profiles were obtained with the shipboard CTD, providing a correction for ray bending for each beam. Depth is estimated from each beam by using the two-way travel time and the known beam angle known, and taking into account the ray bending due to refraction in the water column by sound speed variations. Combining phase and amplitude is used to provide measurement accuracy practically independent of the beam pointing angle.
Responsible persons during this cruise / PI: Achim Kopf (akopf@marum.de) & Ingo Grevenmeyer (igrevemeyer@geomar.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 5.6, open source software distributed from the MBARI and L-DEO web sites, 2000-2012.) was utilized for this purpose. The data was corrected for the roll movement of the vessel. There were no tide, pitch and heave corrections. Using Mbeditviz, artefacts were cleaned manually. NetCDF (GMT) grids of the edited data as well as statistics were created with mbgrid. The published bathymetric grid of the EM120 during cruise SO175 has a resolution of 40 m. No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. A higher resolution is, at least partly, achievable. All grids produced are retrievable through the PANGAEA database (www.pangaea.de).
Chief Scientist: Achim Kopf (akopf@marum.de)
CR: https://elib.suub.uni-bremen.de/ip/docs/ELibD1195_228.pdf
CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2003/20050152.htm
Raw data: not yet
Between 12.11.2003 and 30.12.2003, bathymetric data was acquired in the Gulf of Cadiz during the R/V SONNE cruise SO175. The expedition aimed at a better understanding of the interaction between dynamic processes in a seismically active region with slow plate convergence. In the context of earthquake nucleation and subduction zone processes, the multidisciplinary research programme focused on physical and chemical behavior of sediments, pore water and fluids, exploration of the temperature field of the 1755 thrust earthquake event, the quantification of microbial activity, faunal assemblages, gas hydrates and the deployment of a long-term pressure probe. Bathymetric mapping with the multibeam echosounder (MBES) SIMRAD EM120 was utilized to image the nature of the Gibraltar Arc thrust wedge, a proposed subduction zone, and identify possible sampling sites. Sub-bottom profiling, seismic reflection imaging, heat flow measurements, the deployment of an Ocean Floor pore pressure system as well as video-guided systems and coring complemented the research programme.
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 SO175 cruise, the hull-mounted multibeam echosounder (MBES) SIMRAD EM120 was utilized to perform bathymetric mapping. It allows to conduct surveys in water depths of up to 11,000 m. Two transducer arrays transmit frequency coded acoustic signals (11.25 to 12.6 kHz). Data acquisition is based on successive emission-reception cycles of the signal. While the emission beam has a dimension of 150° across and 2° along track, the reception is obtained from 191 overlapping beams with widths of 2° across and 20° along track. The beam footprint has a dimension of 2° by 2°. The beam spacing can be set to equidistant or equiangular. For further information on the system, consult: https://www.km.kongsberg.com/
During the cruise, an opening angle of 60-70° was used depending on the state of the sea, restricting the coverage to a maximum 14 km wide swath to gain a more continuous spacing of beams on the ocean floor. The spacing within these limits was controlled automatically by the echosounder system.
To convert the recorded travel times into water depth, several sound velocity profiles were obtained with the shipboard CTD, providing a correction for ray bending for each beam. Depth is estimated from each beam by using the two-way travel time and the known beam angle known, and taking into account the ray bending due to refraction in the water column by sound speed variations. Combining phase and amplitude provides measurement accuracy practically independent of the beam pointing angle.
Responsible person during this cruise / PI: Ingo Grevenmeyer (igrevemeyer@geomar.de) & Achim Kopf (akopf@marum.de)
Chief Scientist: Achim Kopf (akopf@marum.de)
CR: https://elib.suub.uni-bremen.de/ip/docs/ELibD1195_228.pdf
CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2003/20050152.htm
Swath sonar bathymetry data used for that dataset was recorded during RV SONNE cruise SO175 using Kongsberg EM 120 multibeam echosounder. The cruise took place between 12.11.2003 and 30.12.2003 in the Gulf of Cadiz. The expedition aimed at a better understanding of the interaction between dynamic processes in a seismically active region with slow plate convergence. Bathymetric mapping with the multibeam echosounder (MBES) SIMRAD EM120 was utilized to image the nature of the Gibraltar Arc thrust wedge, a proposed subduction zone, and to identify possible sampling sites. 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 SO175 cruise, 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, while the actual beam footprint is 2° by 2°. Depending on the roughness of the seafloor, the swath width on a flat bottom is maximum six times the water depth. For further information on the system, consult https://www.km.kongsberg.com/.
During the cruise, an opening angle of 135 - 140° was used depending on the state of the sea, though restricting the coverage of the swath to gain a more continuous spacing of beams on the ocean floor. The spacing within these limits was controlled automatically by the echosounder system.
To convert the recorded travel times into water depth, several sound velocity profiles were obtained with the shipboard CTD, providing a correction for ray bending for each beam. Responsible person during this cruise / PI: Achim Kopf (akopf@marum.de) & Ingo Grevenmeyer (igrevemeyer@geomar.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.SVPs taken during this cruise were not sufficient enough to correct the recorded bathymetric data. Therefore 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 by
utilizing 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 SO175 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: Achim Kopf (akopf@marum.de)
CR: https://elib.suub.uni-bremen.de/ip/docs/ELibD1195_228.pdf
CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2003/20050152.htm