RV Tangaroa Voyage TAN2021_V01 EM2040 Multibeam Echosounder Data

This record describes shallow multibeam data collected on RV Tangaroa voyage TAN2021_V01 (NIWA TAN2113), which was carried out on a contract to the CSIRO MNF from 9th November to 4th December 2021. The voyage had two objectives, which were to recover 27 Ocean Bottom Seismometers which had been deployed around Macquarie Island on IN2020_v06, and complete multibeam and sub bottom profiler mapping along the crest of the Macquarie Ridge and collect new multibeam data during transits.The Kongsberg Maritime EM2040 was used to obtain swath bathymetry, backscatter, and water column data in shallower water (20 - 300 m), using Kongsberg Seafloor Information System (SIS) version 4.3.2 acquisition system. The EM2040 is a single RX system, with 256 beams (or 576 beams in dual swath mode), yielding 400 soundings (or 800 soundings in High Density mode). Water column data, which show the received amplitude of the entire water column for each beam, were recorded simultaneoulsy with the multibeam echosounder data. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 129 files totalling 11.6 GB of raw data in this dataset. There are 129 files totalling 152 GB of water column data.Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position.Raw data (*.all files) were processed using QPS Qimera v2.4.2 for bathymetry and QPS Geocoder Toolbox (FMGT) v7.10.0 for acoustic seafloor backscatter. *.gpd files were generated by Qimera for each *.all file after editing. The quality of the bathymetry data was examined, and surfaces of varying resolution generated for each survey area. The data were cleaned in both 2D and 3D manually. Where appropriate a medium spline filter was used. Gridded bathymetric surfaces were projected in WGS84 / UTM zone 57S (EPSG:32757) coordinate reference system at varying resolutions. Bathymetry datasets were collated, and maps produced in ArcGIS Pro v2.8.3.Water column data files (.wcd) were not processed onboard.Additional information regarding this dataset is contained in the "NIWA Voyage Report 2022007WN.pdf". The report is available from Geophysical Survey and Mapping (GSM) group at CSIRO upon request.