Map based index (GeoIndex) gravity anomalies

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.

Date (Creation): 2000

Citation identifier: http://data.bgs.ac.uk/id/dataHolding/13605466

Point of contact

Organisation name	Individual name	Electronic mail address	Role
British Geological Survey	Enquiries	enquiries@bgs.ac.uk	Distributor
British Geological Survey	Enquiries	enquiries@bgs.ac.uk	Point of contact

Maintenance and update frequency: As needed

GEMET - INSPIRE themes, version 1.0

Geology

BGS Thesaurus of Geosciences

UK Location (INSPIRE)
Scottish SDI
Gravity anomalies
Geophysics
Gravity values

dataCentre

Keywords

NERC_DDC

Access constraints: Other restrictions

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

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.

Other constraints: Either: (i) the dataset is made freely available, e.g. via the Internet, for a restricted category of use (e.g. educational use only); or (ii) the dataset has not been formally approved by BGS for access and use by external clients under licence, but its use may be permitted under alternative formal arrangements; or (iii) the dataset contains 3rd party data or information obtained by BGS under terms and conditions that must be consulted in order to determine the permitted usage of the dataset. Refer to the BGS staff member responsible for the creation of the dataset if further advice is required. He / she should be familiar with the composition of the dataset, particularly with regard to 3rd party IPR contained in it, and any resultant use restrictions. This staff member should revert to the IPR Section ( ipr@bgs.ac.uk) for advice, should the position not be clear.

Spatial representation type: Grid

Denominator: 250000

Language: English

Topic category

Geoscientific information

Geographic identifier: GBN
ISO 3166_2 2009 revision

Geographic identifier: GREAT BRITAIN [id=139600]
British Geological Survey Gazetteer: Geographical hierarchy from Geosaurus 1979 creation

End date: 2014-01 Before

Supplemental Information: Data is visible at map scales above 1:250 000 scale.

Unique resource identifier: OSGB 1936 / British National Grid (EPSG::27700)

Distribution format

Name	Version

Distributor contact

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

OnLine resource

Protocol	Linkage	Name
	https://map.bgs.ac.uk/arcgis/services/GeoIndex_Onshore/geophysics/MapServer/WMSServer?	Geophysics map theme

OnLine resource

Protocol	Linkage	Name
	http://mapapps2.bgs.ac.uk/geoindex/home.html?layer=BGSGravAnom	GeoIndex gravity anomalies

OnLine resource

Protocol	Linkage	Name
	http://mapapps2.bgs.ac.uk/geoindex/home.html?layer=BGSGravAnomGrey	GeoIndex gravity anomalies (grey shaded)

OnLine resource

Protocol	Linkage	Name
	http://mapapps2.bgs.ac.uk/geoindex/home.html?layer=BGSGravCol	GeoIndex gravity anomalies (colour shaded)

Hierarchy level: Dataset

Other: dataset

Conformance result

Title: INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

Date (Publication): 2011

Explanation: See the referenced specification

Pass: No

Conformance result

Title: Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services

Date (Publication): 2010-12-08

Explanation: See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:323:0011:0102:EN:PDF

Pass: No

Statement: 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. Line intersection errors between crossing lines and overlapping surveys have been dealt with 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.