Date (Publication)

2010-05-02

Citation identifier

British Geological Survey / BGS_CMD_REF657

Point of contact

Organisation name	Individual name	Electronic mail address	Role
British Geological Survey (BGS)		enquiries@bgs.ac.uk	Custodian
CADW		offshoredata@bgs.ac.uk	Originator

Maintenance and update frequency

Not planned

Keywords

• NDGO0001

GEMET - INSPIRE themes, version 1.0

• Geology

SeaVoX Vertical Co-ordinate Coverages (L131)

• soil and sediment
• crust

SeaDataNet Parameter Discovery Vocabulary (P021)

• Magnetics
• Side-scan sonar

Access constraints

Other restrictions

Access constraints

No restrictions, a copyright acknowledgement is required and permission from any third party for the release of the data has been obtained. Inclusion of any third party data will determine the copyright acknowledgement that needs to be made.

Use constraints

Other restrictions

Other constraints

The copyright of materials derived from the British Geological Survey's work is vested in the Natural Environment Research Council [NERC]. No part of this work may be reproduced or transmitted in any form or by any means, or stored in a retrieval system of any nature, without the prior permission of the copyright holder, via the BGS Intellectual Property Rights Manager. Use by customers of information provided by the BGS, is at the customer's own risk. In view of the disparate sources of information at BGS's disposal, including such material donated to BGS, that BGS accepts in good faith as being accurate, the Natural Environment Research Council (NERC) gives no warranty, expressed or implied, as to the quality or accuracy of the information supplied, or to the information's suitability for any use. NERC/BGS accepts no liability whatever in respect of loss, damage, injury or other occurence however caused.

Use limitation

unrestricted use, copyright acknowledgement - Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced Cadw materials "Contains Cadw materials ©Crown Copyright [year]"

Spatial representation type

Grid

Distance

5  urn:ogc:def:uom:EPSG::9001

Language

English

Topic category

• Geoscientific information

Geographic identifier

Lundy

BGS Gazetteer 2025-05-07 revision

Geographic identifier

Cardigan Bay

BGS Gazetteer 2025-05-07 revision

Geographic identifier

Western Channel & Celtic Sea

Charting Progress 2: Regional Sea Boundaries 2009-06-18 creation

Geographic identifier

Irish Sea

Charting Progress 2: Regional Sea Boundaries 2009-06-18 creation

Geographic identifier

CELTIC SEA

The SeaVoX Salt and Fresh Water Body Gazetteer: Sub-Ocean Category 1954-01-01 creation

Geographic identifier

IRISH SEA

The SeaVoX Salt and Fresh Water Body Gazetteer: Sub-Ocean Category 1954-01-01 creation

Begin date

2010-04-17

End date

2010-05-02

Reference system identifier

OGP / urn:ogc:def:crs:EPSG::4326

www.epsg.org 2005 revision

Distribution format

Distributor contact

Organisation name	Individual name	Electronic mail address	Role
British Geological Survey (BGS)		enquiries@bgs.ac.uk	Distributor

OnLine resource

Protocol	Linkage	Name
HTTP	http://mapapps2.bgs.ac.uk/geoindex_offshore/home.html?cruise=WESSEX5	BGS Offshore Geoindex

Hierarchy level

Dataset

Statement

Geophysical equipment types used included: Magnetometer and Sidescan Sonar. Wessex Archaeology was contracted to undertake the survey on behalf of CADW. Positions were provided using Leica 500 Trimble RTK beacon receiving corrections via satellite or a Trimble DGPS, which received differential corrections via land stations to provide a position to within 0.6m. Positions were recorded using World Geodetic System 1984 (WGS84) Datum and projected as Universal Transverse Mercator (UTM) Zone 30 North co-ordinates. The navigation data were recorded using Hypack (2008 v.2). The sidescan sonar data were acquired with a Klein 3900 towfish system. This system uses the latest technology in digital sidescan sonar imaging and can operate at either low (445kHz) or high (900kHz) frequency to provide high resolution images. The data were digitally recorded in xtf format using SonarPro Software. The sidescan sonar towfish layback values were recorded on survey logs and also applied to the raw data in SonarPro as it was recorded. The magnetic gradiometer data were acquired using Geomatrix’s G882 gradiometer system consisting of two marine caesium vapour magnetometers arranged horizontally 1.5m apart on a transverse gradiometer tow frame. The gradiometer frame was deployed independently of the sidescan sonar system, permitting the separate adjustment of fish heights. A fin and lead weight positioned under the centre of the frame were used in addition to those attached to each of the magnetometers in order to aid the submersion and stability of the gradiometer. This system was chosen for its high performance in shallow water with high sensitivity and fast sampling rate with a resolution of 0.02nT at 0.1 second sample interval and an absolute accuracy of <3nT throughout the range. The system only suffers a heading error of +/- 1nT error through a 360° arc. The gradiometer data were recorded in Geomatrix software Maglog and exported into ASCII files in real-time, where the raw and corrected position, field value, altitude and depth for each of the magnetometers were recorded in a single string. All magnetometer layback values were applied to the raw data in Maglog during recording and detailed on survey logs. In cases where the layback calculation failed the gradiometer data were corrected during the processing stages.

Metadata

File identifier

c5bc60cd-04eb-3862-e044-0003ba9b0d97 XML

Metadata language

English

Hierarchy level

Dataset

Date stamp

2025-05-07

Metadata standard name

MEDIN Discovery Metadata Standard

Metadata standard version

Version 2.3.5

Metadata author

Organisation name	Individual name	Electronic mail address	Role
British Geological Survey (BGS)		enquiries@bgs.ac.uk	Point of contact