Gausepohl, Florian; Hennke, Anne; Schoening, Timm; Köser, Kevin; Greinert, Jens; Steinführer, Anja (2019): Merged and geo-referenced bathymetric raster from AUV MBES surveys during SONNE cruise SO242/1 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.905580,

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In supplement to: Gausepohl, Florian; Hennke, Anne; Schoening, Timm; Köser, Kevin; Greinert, Jens (2020): Scars in the abyss: reconstructing sequence, location and temporal change of the 78 plough tracks of the 1989 DISCOL deep-sea disturbance experiment in the Peru Basin. Biogeosciences, 17(6), 1463-1493, https://doi.org/10.5194/bg-17-1463-2020

This dataset is a bathymetric raster (GeoTIFF, UTM 16S) with a 2 x 2 m resolution merged from three different AUV MBES surveys (Abyss192 - SO242/1_047-1; Abyss193 - SO242/1_060-1; Abyss194 - SO242/1_069-1) conducted during cruise SO242_1 with the German RV SONNE. It includes the entire DEA in the center and extends towards a mountain area NE of the DEA. The provided raster is corrected for lateral and vertical offsets based on the ship-acquired MBES (Kongsberg EM122 mounted in RV SONNE) dataset (https://doi.pangaea.de/10.1594/PANGAEA.905579) as reference layer.

The data were acquired by AUV ABYSS (Type REMUS 6000) equipped with a RESON Seabat 7125 MBES (200 kHz, 1° by 2° beam angle). The MBES survey altitude was 80 m. The raw data (.s7k) were processed with MB-system (Caress, D.W., and D.N. Chayes, Open source software distributed from the MBARI and L-DEO web sites) using the "mbedit" command for a rough correction of erroneous depth measurements and "mbnavadjust" for the relative and absolute navigation correction. The data were then transferred to the QPS processing software Qloud for further data cleaning and finally exported as point cloud. The bathymetric data from each survey were gridded (2x2 m) and merged into one bathymetric raster using ArcGIS.

The merged AUV bathymetric data with a spatial resolution of 2 m was resampled to match the 38 m resolution of the ship-based bathymetric raster enabling a direct grid comparison and correction of vertical and lateral offsets of the AUV bathymetric grid relative to the ships data layer. Using 5 m contour lines to visualize morphological features in the area, the 38 m AUV bathymetry was shifted/stretched manually onto the EM122 data using the ArcGIS 10.2 Georeferencing Toolbox for geographic corrections (contour lines were derived with the Spatial Analyst Toolbox and grids were subtracted to see z-offsets using the Raster Calculator function). The derived vertical offset of -9 m between the ship- and the AUV-acquired bathymetric data was added to the depth values of the AUV MBES data.