Wintersteller, Paul; Kammann, Janina; Strack, Anne; Geissler, Wolfram H (2019): Composite Grid (DTM) and Backscatter Mosaics of EM120 and EM122 Multibeam Echosounder (MBES) Bathymetry of Cruises MSM20-2 and MSM24 around Tristan da Cunha [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.898303,

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In: Geissler, Wolfram H; Wintersteller, Paul; Strack, Anne; Kammann, Janina; Jegen, Marion; Maia, Marcia; Schloemer, Antje; Jokat, Wilfried (2019): GIS based analysis, processed sub bottom profiler, and composite grid and backscatter mosaics around Tristan da Cunha [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.906154

The bathymetric grids and backscatter mosaics are created based on data recorded during RV MARIA S. MERIAN cruises MSM20-2 and MSM24 in 2012 & 2013 around Tristan da Cunha. Postprocessing and creation of products were conducted by Janina Kammann (University Hamburg), Anne Strack (University Bremen / MARUM) and the Seafloor-Imaging & Mapping group of University Bremen / MARUM, 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, 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. CTD measurements were taken during the cruise, and these were sufficient to represent the changes in the sound velocity throughout the study area. Further roll, pitch and heave corrections were not applied for the MSM20-2 and MSM24 data. Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. With mbmosaic one creates tables of the average amplitude and/or sidescan values as a function of the grazing angle with the seafloor that can be used by the program mbprocess to correct the sidescan or amplitude data for the variation with grazing angle. 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 & backscatter mosaic grid of the cruise have a resolution of 50 m. If present, the grid extended with _num represent a raster dataset with the statistical number of beams/depths taken into account to create the depth of the cell. The extended _sd -grid then contain the standard deviation for each cell. All grids produced are retrievable through the PANGAEA database (www.pangaea.de). Backscattter - Beam Time Series Mosaic A composite mosaic from both cruises, MSM20-2 and MSM24, of the so called pseudo-side-scan or beam time series data were created with the software package QPS Fledermaus FMGT ™ v.7.7.2 (Geocoder Toolbox) in order to be compared with the results of MB-System. Although data of ship-turns are emphasized in FMGT results, most probably due to issues with the yaw-stabilization/compensation, the results seemed to have more detailed information in comparison to the MB-System results and were therefore taken into account for our publication. The reason eventually could be traced back to a more accurate Tx/RX, time and angular varying gain correction during post processing. To unify the grid and mosaicing outputs we currently provide them in ESRI ASC format projected in UTM28S - WGS84. The data is zipped (zip).