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.

 
Citation proposal
British Geological Survey. Map based index (GeoIndex) gravity anomalies. https://services.mspdata.eu:/geonetwork/srv/api/records/9df8df53-2a94-37a8-e044-0003ba9b0d98

Simple

Date ( Creation )
2000
Identifier

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

  Custodian

  Originator

  Distributor

  +44 115 936 3276 
Maintenance and update frequency
asNeeded As needed
GEMET - INSPIRE themes
  • Geology
BGS Thesaurus of Geosciences

  • Geophysics

    ,

    Gravity anomalies

    ,

    Gravity values

Keywords

  • NERC_DDC

Use limitation

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.

Access constraints
otherRestrictions Other restrictions
Other constraints

otherRestrictions

Denominator
250000
Metadata language
English English
Topic category
  • Geoscientific information
Geographic identifier

GBN

 

Date ( Revision )
2009

Geographic identifier

GREAT BRITAIN [id=139600]

 

Date ( Creation )
1979

N
S
E
W


Supplemental Information

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

Reference system identifier

OGP

/

urn:ogc:def:crs:EPSG::27700

 

Date ( Revision )
2005

Distribution format

  • Unknown

    (

    Unknown

    )

  Distributor

  +44 115 936 3276 
OnLine resource
Gravity anomalies  
OnLine resource
Geophysics map theme  

The wms layer for 'GeoIndex gravity anomalies' is held within the 'Geophysics' theme WMS layer which this URL connects to.

OnLine resource
Geophysics map theme  

The user will need to select 'Map layers' from the top left menu and select the 'Gravity anomalies' check box from the drop down menu to view the data.

Hierarchy level
dataset Dataset
Other

dataset

Conformance result

Date ( Publication )
2011
Explanation

See the referenced specification

Pass
false

Conformance result

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
false
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.

Metadata

File identifier
9df8df53-2a94-37a8-e044-0003ba9b0d98   XML
Metadata language
English English
Hierarchy level
dataset Dataset
Date stamp
2017-01-17
Metadata standard name

NERC profile of ISO19115:2003

Metadata standard version

1.0

  Point of contact

Dataset URI

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

 
 

  Overviews


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