CP2 Regional Sea Boundaries: Western Channel & Celtic Sea, Offshore 1:250k: Little Sole Bank, SeaVoX Sub-Ocean: CELTIC SEA, NORTHEAST ATLANTIC OCEAN (40W)
The survey was led by the Joint Nature Conservation Committee, in collaboration with the Marine Institute, the British Geological Survey and the University of Plymouth. Defra Natural Environment Group Science Division (CRO 361) made a significant contribution to this work. This work contributed to the MESH project (www.searchmesh.net). The MESH Project ran between 2004 and 2008 and was made up of a consortium of twelve partners from five European countries led by the UK’s Joint Nature Conservation Committee (JNCC), with financial support from the EC’s INTERREG IIIB NWE Programme. The MESH partnership drew together scientific and technical habitat-mapping skills, expertise in data collation and its management, and proven practical experience in the use of seabed-habitat maps for environmental management within national regulatory frameworks. The aims of the R/V Celtic Explorer cruise (CE0705) on 4th-18th June 2007 were to acquire high resolution multibeam, sub-bottom profiler and camera data in the SW Approaches area, located approximately 320km southwest of Land's End. The cruise not only mapped the variable morphology of the SW Approaches area, but also investigated the biological communities within the canyon system for the assessment of potential Special Areas of Conservation (SAC) under the EC Habitats and Birds Directive (Annex I) (Johnston et al. 2002). The cruise also tested the application of the survey standards and protocols developed under the MESH project. The cruise was the first thorough test for the recently completed MESH Guidance Framework, providing a 'proof of concept' from planning to completion. The backscatter and geophysics data are archived and available for download at the British Geological Survey (BGS) MEDIN Data Archive Centre (DAC) for Geology and Geophysics. Biological and bathymetry data are archived at DASSH and UKHO respectively. Technical details of the survey are contained in BGS Commissioned Report CR/07/123N (http://nora.nerc.ac.uk/id/eprint/507379/). Final Report (http://nora.nerc.ac.uk/id/eprint/507378/). GeoIndex Offshore - https://mapapps2.bgs.ac.uk/geoindex_offshore/home.html?cruise=2007/6_MESH&.
Navigation: Fugro Starfix-HP (High Precision) GPS positioning system. All data acquisition systems took their time stamp from this navigation signal. The Starfix HP performed well during operations with only one significant occurrence of loss of navigation from 03:27 to 04:54 on the 9th June 2007 during seismic data acquisition on line 4. Some problems were experienced with the USBL system, particularly towards the latter half of the cruise. Multi-tip Sparker System: Source: EG&G, nine candle, multi-tip array with 135 tips. At times during the course of this cruise, it was sufficient to only operate with 90 tips. Power is supplied from an Applied Acoustic Engineering CSP-D HV Bangbox, running at 1000 Joules per shot on lines 1-7, 1250 Joules per shot on lines 8-11, 750-1500 Joules per pulse on line 12 and 1500 Joules per shot on lines 13-16. The CSP-D utilised the ship's main 240V 'domestic' power on a 16A circuit breaker. The Sparker was fired once every 6 seconds, interleaved with the Deep-Tow Boomer firing. Hydrophone: SIG 7 channel, 10m hydrophone streamer and SIG preamplifier with all channels summed to give a single channel output. The summed output was fed into the British Geological Survey (BGS) own designed amplifier that incorporates low pass and anti-alias filters and manually adjustable analogue gain to compensate for acoustic losses with water depth. For the Sparker system the bandpass filter is between 100 and 1730 Hz. Recording: The recording system is a CODA DA200 with twin displays and set up to digitally record two seismic sources simultaneously, in this case the Sparker and Deep Tow Boomer. The output data was stored in CODA and SEGY format. The Sparker signal was sampled at 5000Hz. Deep Tow Boomer System: Source: The Deep Tow Boomer system is a towed negatively buoyant fish comprising a 'boomer plate' transducer, high voltage storage and discharge system, a short hydrophone streamer and various sensors and controls. The high voltage power is supplied by a 240VAC to 6000VDC transformer on the vessel. The Deep Tow Boomer was generally fired 3-4 times in every 6 seconds, depending on water depth and the height of the tow fish from the seabed, interleaved with the Sparker firing. Hydrophone: A 2m, 6 element deep water BGS streamer was used during this cruise. The amplifier incorporates low pass and anti-alias filters and manually adjustable analogue gain to compensate for acoustic losses with water depth. For the Deep Tow Boomer the bandpass filter is between 450 and 4500 Hz. Recording: CODA DA200 system. The Deep Tow Boomer signal was sampled at 10,000Hz. Multibeam: Simrad EM1002 system is designed for high-resolution sea bed mapping in water depths of less than 1000 m. The hull-mounted system operates at a frequency of 93-95 kHz. A fixed swath coverage of 660m was utilised throughout, to maintain a beam spacing of at least 5% of water depth, providing the acceptable data density and data quality. Processing was carried out onboard using CARIS HIPS and SIPS and a variety of output formats were produced including the processed xyz files, ArcGIS raster files, Geotiffs and Fledermaus files. Precision Echo Sounder (EA600): The Simrad EA600 single beam system is a multi frequency hydrographic echo sounder. The three main frequencies are 12kHz, 38kHz and 200kHz with the shared transducer at 120kHz. Seatronics DTS 6000 Drop Frame Camera: The Seatronics drop frame system was deployed from the starboard side of the vessel. The system comprised a 5 mega pixel Kongsberg and Imenco digital stills camera, and an integrated DTS 6000 digital video telemetry system. Sensors monitored depth, altitude and temperature. A USBL beacon provided positional information for 14 camera tows, however, for the latter 30 tows the USBL was not working and vessel position was used.
unrestricted use, copyright acknowledgement
Geophysical, Multibeam, Photo and Video Survey 2007/6_MESH: 2007 MESH SW Approaches Canyons Survey (04/Jun/2007 to 18/Jun/2007)
Available under the Creative Commons Licence subject to the following acknowledgement accompanying the reproduced Department for Environment, Food and Rural Affairs, Joint Nature Conservation Committee, Marine Institute, British Geological Survey, University of Plymouth materials "Joint copyright ©2007 Defra, JNCC, Marine Institute, BGS, University of Plymouth"