DOI: 10.1594/pangaea.900980
title: Gridded bathymetry from EM122 multibeam echosounder of RV Sonne cruise SO266 (offshore SW Taiwan)

description: During the RV Sonne cruise SO266, which took place between 15.10.2018 to 18.11.2018, bathymetry data based on multibeam echosounder (MBES) was recorded. The research area is located in the SW off Taiwan. The main focus of the cruise was the investigation of gas hydrate distributions influenced by different tectonic settings (at active and passive margins) and lithologies using the MEBO200 to collect sediment samples. The ship-mounded multibeam echosounder was used to collect detailed information about the drill sites containing bathymetry and backscatter data as well as water column information. Additionally it was accomplished to create a detailed map (5-15 m grid cell size) of the region SW off Taiwan, which shows structural features of the passive and active continental margins as well as gas hydrate linked morphologies such as mud volcanoes. The KONSBERGER EM710 was used in addition to the KONGSBERG EM122 to map the continental slope.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 RV SONNE cruise SO266 the hull-mounted KONGSBERG EM122 multibeam echosounder systems was used in the areas of interest. This echosounder system uses nominal sounding frequencies of 10.5 to 13 kHz and was therefore used in water depth of more than 700 m. 288 beams with an acoustical footprint of 0.5°(TX)/1°(RX) are formed for each ping. Due to the use of the high-density equidistant and dual swath mode 864 soundings were received with every ping. During the cruise the swath width was set to 120° and partly to 130°. For further information consult https://www.km.kongsberg.com/. The EM122 was recording continuously during the cruise. To avoid signal interferences all used hydroacoustic systems were synchronized using the on-board K-Sync-Unit. During the hydroacoustic surveys the vessel speed was conducted to 11 kn. The vessel velocity was lowered to 3 kn for flare imaging surveys. The data quality was generally good, due to the good signal to noise ratio of the research vessel.Responsible person during this cruise / PI: Paul Wintersteller (pwintersteller@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. CTD and XCTD measurements were done between or during the MBES surveys to receive sound velocity profiles (SVP), which were applied during the acquisition of the hydroacoustic data. Roll, pitch and heave corrections were not applied for the SO266 data. Using Mbeditviz, artefacts were cleaned manually. NetCDF (GMT) grids of the edited data as well as statitics were created with mbgrid. The published bathymetric grid of the cruise SO266 has a resolution of 25 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. All grids produced are retrievable through the PANGAEA database (www.pangaea.de).Chief Scientist: G. Bohrmann (gbohrmann@marum.de) CR: not yet CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2018/20180051.htm A special thanks goes to the following watchkeeper during SO266: W. Cheng, J. Elger, H. HsuFinal processing has been supported by Anne Strack & Nontje Rücker as student assistants.