CP2 Regional Sea Boundaries: Minches & Western Scotland, Offshore 1:250k: Great Glen, Sutherland, SeaVoX Sub-Ocean: INNER SEAS OFF THE WEST COAST OF SCOTLAND
This British Geological Survey (BGS) marine geophysical and multibeam survey took place in July 2005 in the Summer Isles region and Loch Broom and Little Loch Broom aboard the RV Calanus. The survey was a part of the BGS Offshore Mapping and Modelling Project, North Atlantic Correlation. Subsurface seismic data were gathered using a Surface Tow Boomer. Multibeam bathymetry data was collected using a Geoacoustics GeoSwath system supplied and operated by Fathoms Ltd. All of the data were recorded digitally, but paper records were generated also. The data are archived by BGS. Backscatter and geophysical data are available for download. Technical details of the survey are contained in BGS Report IR/05/139 (http://nora.nerc.ac.uk/id/eprint/11140/). GeoIndex Offshore - https://mapapps2.bgs.ac.uk/geoindex_offshore/home.html?cruise=2005/4&.
NAVIGATION: Differential GPS, all position data are referred to the WGS 84 datum. For the swath bathymetry survey the DGPS receiver was supplied by Fathoms and input directly to the Geoswath system. For the surface tow boomer operations the ship’s DGPS system was used. SURFACE TOW BOOMER:Source: EG&G plate in Applied Acoustics catamaran. High Voltage Power Supply: 2 x Applied Acoustic Engineering CSP3000 capacitor charging units, (1 plus a spare). This unit was powered from the ship’s mains and with a switchable output up to a maximum of 2.2 KJ, maximum used for the S.T.Boomer was 300J at a repetition interval of 0.3 seconds. Hydrophone: 2 x Teledyne, 10 m, 7 channels with all summed to give a single output, (1 plus a spare). The summing amplifier used was a newly developed BGS unit, which also included low pass and anti-alias filters. The new unit proved to be significantly less noisy than the previous version, a feature which was particularly noticeable in deep water when very high gain levels were required. Recording: CODA DA200 four channel digital recording and processing system, with the data being recorded on harddisk in CODA format and backup to Exabyte tape in both SEGY and CODA formats. The data were recorded with a sampling frequency of 12kHz, record length of 200mseconds and a bandpass filter of 450-4500Hz. The start of recording was delayed in deep water to maximise the usable data record below the sea bed. Position was recorded with every shot. On-line processing: CODA system. SWATH BATHYMETRY: Geoacoustics GeoSwath system, contractor Fathoms Ltd. A TSS DMS25 Motion Sensor, a mini-SV probe and a Tritech single beam echosounder, to measure the depth directly below the transducers, were all mounted in the transducer head assembly. Additionally, input from a gyrocompass and differential GPS were also required and these were supplied by a TSS Meridian gyrocompass and a Trimble DGPS receiver. All positions were corrected to the transducer location so that the processed bathymetry data was correctly located. Data processing: Fathoms personnel used a GeoSwath Plus processing package on a second PC. Bathymetry data is in UTM zone 30N and the backscatter was in UTM zone 29N. Backscatter data: ARCGRID; TIF images. Fledermaus (.sd) available on request. For more detailed information on the acquisition equipment and data collection techniques, operational standards, data processing methods and quality control procedures used on this survey see the Report of Survey/Cruise Report and associated documentation where available. The information available may vary depending on the age of the survey. Data are checked and loaded to the BGS Coastal and Marine data management system following BGS marine data management procedures.
Geophysical and Multibeam Survey 2005/4: Summer Isles / East Minch (04/Jul/2005 to 23/Jul/2005)
unrestricted use, copyright acknowledgement
Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced British Geological Survey materials "Contains British Geological Survey materials ©UKRI [year]"