Map based index (GeoIndex) gravity anomalies

Dataset description

This low-resolution image has been produced from BGS land and marine gravity data. The colour was generated using the BGS COLMAP software package. Colour levels are defined by histogram equalisation. Combining this image with the grey shaded relief image produces a similar image to the colour shaded relief image. The measured gravity values have been corrected in order to show the anomalies attributable to variations in crustal density. In broad terms the blues are attributable to large volumes of low density rocks, the reds to high density rocks. Significant lows occur, for instance, over areas of thick, low density sedimentary rocks(e.g. Cheshire Basin, Wessex Basin), or large granites (eg Cornwall). For marine data, free-air anomalies have been calculated from observed gravity values along marine survey lines. Line intersection errors between crossing lines and overlapping surveys have been used using network adjustment techniques. Free air anomalies have been calculated for sea-bottom stations. For land data, bouguer anomalies have been calculated from gravity observations at points of known height. In order to minimise the effect of topography, Bouguer corrections for the British Mainland have been applied using a density estimated for each station. Elsewhere a correction density of 2.67 Mg/m3 has been used. Corrections for the gravitational effect of terrain have been made where significant, and in a general extent to a radius of 48.6km. The data have been interpolated onto a 1km x 1km grid using a variable tension technique, and smoothed.

Constraints

The usual BGS licensing terms and conditions apply to external use of the data.

Further information

For more information please contact:

Enquiries

Environmental Science Centre, Nicker Hill, Keyworth
Nottingham
NG12 5GG

Tel : +44 (0)115 936 3143
Fax :+44 (0)115 936 3276
Email :enquiries@bgs.ac.uk

 

Further details

Dataset details

Language English
Curator British Geological Survey
Supply media/format Not available
Storage format Digital:ESRI Files
Frequency of update as needed
Start of capture 2000
End of capture Not known
Contact details
Department Enquiries
Organisation British Geological Survey
Address Environmental Science Centre, Nicker Hill, Keyworth
City Nottingham
County Nottinghamshire
Country United Kingdom
Postcode NG12 5GG
E-mail enquiries@bgs.ac.uk
Telephone +44 (0)115 936 3143
Fax +44 (0)115 936 3276
Keywords
Topic category geoscientificInformation (information pertaining to earth sciences)
Keywords and Keyphrases GEOPHYSICS
GRAVITY ANOMALIES
GRAVITY VALUES
Keyword source BGS Keyphrases
Spatial details
Spatial Reference System OSGB 1936 / British National Grid [27700]
Dataset extent
Coverage (Lat/Long) North boundary : 60.84
East boundary  : 2
South boundary : 49.76
West boundary  : -7.56
Metadata
Metadata language English
Metadata last updated 5th June 2014
Metadata standard ISO standard 19115:2003
Copyright and IPR
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.
Location
W -7.56 60.84 N
Extent of coverage for this dataset (shown here as Latitude and Longitude)
S 49.76 2 E