133 publications from this institution
EGU21-2470 https://doi.org/10.5194/egusphere-egu21-2470 EGU General Assembly 2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.
The black coral Anthipatella wollastoni forms marine animal forests in the mesophotic zone. The spatial extent of black coral forests is not well known in many regions. Due to its protein and chitin skeleton, the coral is difficult to image using acoustic remote sensing techniques compared to corals with carbonate skeletons. Several manufacturers have recently introduced an additional data type to their multibeam echosounders, called “multi-detection,” which provides additional target detections per beam in addition to the primary bottom detection. In this study, we used a Norbit chirp multibeam echosounder in multi-detect mode to acquire up to three targets in each beam in an area of black coral below 45 m depth off the coast of Lanzarote (Canary Islands, Spain). Multi-detect allows features above and below the primary bottom detection to be identified without the need to store and process water-column data. Black coral can be detected by comparing “multi-detection” data with ground truthing by technical divers and underwater cameras. However, the repeatability of the detections is limited and further sensitivity studies are required.
Dataset for the study "Can Anthipatella wollastoni be detected in Multibeam Echo Sounder multi-detect data?", currently under review at Frontiers in Remote Sensing. The files include: Photos.zip: GoPro Photos with ground truthing of two ridges with the occurrence of Black Corals. Photos have been geo-located using the coordinates of the onboard Multibeam System and correcting a time offset. Refer to the paper for details. Sound velocities: Sound velocity casts using a Base-X shallow water profiler used to correct the multibeam echo sounder. MD_manual_edit: Shape file including the position of Multi-Detects after the manual cleaning. The MD point objects have been joined with information from the local bathymetry and slope. Note that associated intensity values are erroneous due to a bug in the recording MBES firmware. MBES: Includes Norbit s7k (version 3) raw files of the multibeam echo sounder data (Norbit iwbms-e, Serial number #12). Files in folders with "MD" were used for the Multi-Detect study. Files with "MFE" include multifrequency data. We failed to locate the black corals in multi-frequency backscatter data. Multi-detect data were recorded with a swath width of 100° split into 512 beams. The multifrequency data contains 190 and 370 kHz information. Spreading correction was set to 40, absorption set to 107 dB/km (calculated for the 390 kHz frequency with a mean water temperature of 16°C, a salinity of 35. Actual temperature according to diver information was 24°C at the surface, 23° until 50 m and 21° until 80 m). All offsets have been accounted for during the survey. The data is located using an RTK correction (refer to paper for further details).
The raw data used for the study Seasonal Change of Multifrequency Backscatter in three Baltic Sea Habitats by Schulze et al.; currently under review at Frontiers in Remote Sensing. Files are stored in the s7k-Format, and sorted by date of acquisition and frequency. 200 and 400 kHz data were manufacturer-calibrated. Correct absorption values have been applied duirng the export. Refer to the paper for further dataset information. This upload stores the 700 kHz data recorded in October 2019.
