Alternate title

newGIP v7 2015

Date (Creation)

2015-05-22

Citation identifier

http://data.bgs.ac.uk/id/dataHolding/13606634

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

Biannually

GEMET - INSPIRE themes, version 1.0

• Geology

BGS Thesaurus of Geosciences

• UK Location (INSPIRE)

• Natural hazards

dataCentre

• UK Location (INSPIRE)

Keywords

• NERC_DDC

Access constraints

Other restrictions

Other constraints

This information has commercial potential and access should be subject to the Programme Manager's approval (Kathryn Lee). The information should not be used to indicate actual hazard at a site. It does not assess if the hazard is actually present. This can only be determined by a site specific assessment.

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

The dataset is made available to external clients under BGS Digital Data Licence terms and conditions. Revert to the IPR Section ( iprdigital@bgs.ac.uk) if further advice is required with regard to permitted usage.

Spatial representation type

Vector

Denominator

50000

Language

English

Topic category

• Geoscientific information

Geographic identifier

ENG

ISO 3166_1 alpha-3 2009 revision

Geographic identifier

ENGLAND [id=150000]

British Geological Survey Gazetteer: Geographical hierarchy from Geosaurus 1979 creation

Geographic identifier

SCOTLAND [id=140000]

British Geological Survey Gazetteer: Geographical hierarchy from Geosaurus 1979 creation

Geographic identifier

SCT

ISO 3166_1 alpha-3 2009 revision

Geographic identifier

WALES [id=170000]

British Geological Survey Gazetteer: Geographical hierarchy from Geosaurus 1979 creation

Geographic identifier

WLS

ISO 3166_1 alpha-3 2009 revision

End date

2015 Before

Supplemental Information

The methodology behind the DPD involves balancing the 6 GeoSure natural ground stability hazards against each other. The GeoSure maps themselves have a fivefold coding (A to E), and the balancing exercise involves comparing each level across the six hazards e.g. comparing a level C shrink-swell clay area with a level C running sand area. The comparison is done by estimating how frequently a ground movement event may occur that could have the potential to damage a property (in particular, low-rise buildings). Each level of each of the hazards is given an 'occurrence factor' (as shown in Table 1 of the user guide), which can then be added together to derive a Total Occurrence Factor at a particular location (e.g. within a given postcode). In 2003, the BGS also published a series of GIS digital maps identifying areas of potential natural ground movement hazard in the UK, called GeoSure. There are six separate hazards considered - shrink-swell clays, slope instability, dissolution of soluble ground, running sand, compressible ground and collapsible ground. These maps were derived by combining the rock classification scheme (RCS) information from DiGMapGB-50 with a series of other factors which may cause the geological hazards (e.g. steep slopes, groundwater). In 2007, the BGS used the GeoSure maps to make an interpretation of subsidence insurance risk for the UK property insurance industry, released as the new GeoSure Insurance Product. This represents the combined effects of the 6 GeoSure hazards on (low-rise) buildings in a postcode database - the Derived Postcode Database, which can be accompanied by GIS maps showing the most significant hazard areas. The combined hazard is represented numerically in the Derived Postcode Database as the Total Occurrence Factor, with a breakdown into the component hazards, as described in more detail below. GeoSure Derived Postcode Database (DPD) The DPD is a stand-alone database, which can be provided separately to the visualisation layers in the Full GeoSure Insurance Product.

Unique resource identifier

OSGB 1936 / British National Grid (EPSG::27700)

Distribution format

Name	Version
Postcode Database	Current BGS version
ESRI Shapefile	Current BGS version
Map Info File	Current BGS 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
	http://www.bgs.ac.uk/products/geohazards/geosureInsurance.html

Hierarchy level

Dataset

Other

dataset

Statement

In detail, the methodology behind producing the DPD is as follows: 1. The postcode centroids layer, as supplied by Ordnance Survey, is buffered using a value of 300 metres. This value takes into account the variability in size of postcodes (250 metres) and the 50 metres cartographic precision of the Digital Geological Map of Great Britain at the 1:50,000 scale (DiGMapGB-50) data that is used as the geological basis for the GeoSure hazard layers. 2. An 'occurrence rating' is then assigned to each of the A-E levels of each master GeoSure hazard layer. These occurrence ratings represent how frequently a ground movement event may occur that could have the potential to damage a property (in particular, low-rise buildings). The occurrence ratings are then multiplied by a nominal score (100) in order to derive a series of 'unified ratings'. Before use in the DPD, these unified rating values in the table are then multiplied by 10 allow the use of integer values. For example a class 'D' shrink-swell pixel will have a value of 10 x 10 = 100. 3. Zonal statistics are then calculated using the buffered postcode layer from above in conjunction with each of the six GeoSure hazard grids (25m pixel size). This process considers each hazard in turn and calculates the average of the pixel values that occur within each of the buffered postcodes (circular areas). As each pixel covers the same area the resultant average represents the area-weighted average of the hazard values within the circular area. These average values for each hazard are added to the output Derived Postcode Database as 'occurrence factors'. 4. The six hazard occurrence factors for each postcode are summed and added to the DPD as column Total_of (Postcode Total Occurrence Factor, PTOF). 5. The Total_of column is classified into 5 classes divided into 5 equal categories as shown in table 3 of the newGeoSure Insurance Product: Methodology report. (IR/12/074). This classification is added as column Class5 with values of 1-10. This, and the Class5 split, is done in order to allow easier interpretation and visualisation of the total hazard if required (for example, Class5 can be used to colour up the postcode centroid in the GIS to show how the total hazard varies across an area).

Metadata

File identifier

16f8a3dc-9ea3-333e-e054-002128a47908 XML

Metadata language

English

Hierarchy level

Dataset

Date stamp

2025-05-06

Metadata standard name

UK GEMINI

Metadata standard version

2.3

Metadata author

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

Dataset URI

http://data.bgs.ac.uk/id/dataHolding/13606634