British Geological Survey (BGS) Geophysical and Multibeam Survey 2006/2: North West Scotland, CD180 (20/May/2006 to 09/Jun/2006)

Geophysical equipment types used included: Airgun/Sleeve Gun, Echo Sounder, Gravimeter, Magnetometer, Pinger and Sparker. The survey was undertaken by British Geological Survey. NAVIGATION: vessels Trimble DGPS system, WGS84. AIRGUN: Source: An array of 5 x 40 cu inch Bolt 600B airguns with waveshape kits and time break solenoids. Hydrophone (receiver): A 4 channel SIG hydrophone summed to give a single channel 32m active length. Recording: The BGS CODA DA200, software version 3.9.11.5L(3360) 2005 four-channel digital recording and processing system was utilised to record the raw data. The data were recorded to Flipdisks in CODA format with a sampling frequency of 3kHz, record length of 4 seconds and bandpass filter of 25-800 Hz. The start of recording was delayed in deep water to permit a minimum of 2 seconds of data below the sea-bed. The CODA system also received a navigation data string from the vessels Trimble DGPS system, and logged position, time and date for each shot. On line processing: the CODA system was also used to process the data on-line and produce a real time hard copy output on an Ultra 120 thermal printer. Processes applied were time varied gain (TVG), time varied filtering (TVF) and trace mixing and, in extremely large amplitude sea swell situations, a swell filter. Both TVG and TVF were applied from the sea-bed, which was tracked automatically. A 1.5 sec record length was used for the on-line hard copy, with a delay adjusted to give an optimum record for the water depth. SPARKER: Source: EG&G, nine candle, multi-tip sparkarray with 135 tips. High Voltage Power Supply: An Applied Acoustic Engineering CSP2200 capacitor charging unit. This is a single unit, powered from the ship’s 240VAC supply incorporating switchable output energy up to a maximum of 2200 J. Apart from lines 2-5 (1800J) the whole survey was conducted at an output of 2200 J. Hydrophone (receiver): A seven channel Teledyne 10m hydrophone, summing on the most part, all channels to give a single output. Recording: same system as the airgun, the data were recorded with a sampling frequency of 5kHz, record length of 1.9 seconds and a bandpass filter of 100-1730 Hz. The start of recording was delayed in deep water to permit a minimum of 1 second of data below the seabed. On-line processing: The sparker data was processed on line for QA purposes of the recorded data. Processes applied were time varied gain (TVG), time varied filtering (TVF), swell filter (occasionally), and trace mixing. GRAVITY METER: ZLS Corporation UltraSys controlled LaCoste and Romberg sensor serial No. S75 system. MAGNETOMETER: Barringer proton precession magnetometer with a 1 gamma sensitivity. The sensor was towed 200 m astern to minimise the effects of the vessel’s steel hull on the local magnetic field. MULTIBEAM: Simrad EM12 multibeam system. Several sound velocity profiles were made throughout the survey, Rockall Bank, before the start of line 12 and the Faroe Bank Channel. It was noted that the Faroe Bank Channel had fresh water close to the seabed. Calibration issue during survey. Backscatter file type: TIF. PINGER: 3.5kHz pinger is a transducer mounted in a tow fish and was towed over the starboard side. This was controlled by an IOS transceiver with the data recorded on a CodaOctopus360 acquisition system and was part of the standard shipboard equipment. PRECISION ECHOSOUNDER: 10kHz IOS transducer mounted in a tow fish and deployed off the port side close to amidships. This is controlled by a Simrad EA500 transceiver and display and was compensated for fish height with the depth recorded centrally. 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.

Minimal Distance: 5 urn:ogc:def:uom:EPSG::9001

INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of unknown theme