OR/15/021 About the GeoSure Insurance Product (GIP) dataset
| Wildman, G, Adlam, K A M and Cartwright, C E. 2015. User Guide for the GeoSure Insurance Product (version 7). British Geological Survey Internal Report, OR/15/021. |
Dataset introduction
The GeoSure Insurance Product (GIP) provides the potential insurance risk due to natural ground movement. It incorporates the combined effects of the 6 GeoSure hazards on (low-rise) buildings and links these to a postcode database — the Derived Postcode Database. A series of GIS (Geographical Information System) maps show the most significant hazard areas. The ground movement, or subsidence, hazards included are landslides, shrink-swell clays, soluble rocks, running sands, compressible ground and collapsible deposits.
This document accompanies the latest Version 7 release (May 2015) of the GeoSure Insurance Product and included Derived Postcode Database.
For more information on the full GeoSure dataset, please refer to the ‘User Guide for the GeoSure dataset (version 7)’.
Background
The GeoSure Insurance Product (including the Derived Postcode Database) represents the end of an interpretation process, starting with the BGS Digital Geological Map of Great Britain at the 1:50 000 scale (called DiGMapGB-50, first released as Version 1 in 2003). This digital map is the definitive record of the types of rocks underlying Great Britain (excluding Northern Ireland), as represented by various layers, starting with bedrock and moving up to overlying superficial layers.
In 2003, the BGS published a series of GIS digital maps identifying areas of potential natural ground movement hazard in the UK, called GeoSure, which are frequently updated. There are six separate hazards considered – shrink-swell clays, landslides, soluble rocks, running sand, compressible ground and collapsible deposits (see Appendix 1 for descriptions of these hazards). 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 2005, BGS used the GeoSure maps to make an interpretation of subsidence insurance risk for the British property insurance industry, released as the new GeoSure Insurance Product (GIP). 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. More detail on this is described below.
Who might require this data?
This dataset has been specifically developed for the insurance of low-rise buildings. The GeoSure datasets have been developed to identify the potential hazard for low-rise buildings and those with shallow foundations of less than 2 metres.
What the dataset shows
The full GeoSure Insurance Product comprises six GeoSure Hazard ‘Visualisation’ (HV) layers and the GeoSure Derived Postcode Database (DPD).
GeoSure Hazard ‘Visualisation’ layers
The six HV layers are GIS polygon layers representing where the most significant hazard potential exists. This does not mean that areas outside of these polygons have no hazard potential, only that the hazard potential is less significant. These derived HV layers should not be used on their own as a means of assessing the hazard potential of a specific location. These visualisation layers should ONLY be used in conjunction with the DPD in order to fully assess the hazard potential. These layers are intended to give the user a visual representation of the distribution of significant hazards.
GeoSure Derived Postcode Database
The DPD is a stand-alone database, which can be provided separately to the visualisation layers in the full GeoSure Insurance Product. This product uses Code-Point® Open data to relate postcodes to Ordnance Survey grid references. The use of Code-Point® Open data is governed by the OS OpenData™ licence and is subject to the terms at: https://www.ordnancesurvey.co.uk/business-and-government/licensing/using-creating-data-with- os-products/os-opendata.html. The DPD contains a normalised hazard rating for each of the 6 GeoSure themes hazards (i.e. each GeoSure theme has been balanced against each other) and a combined unified hazard rating for each postcode in Great Britain.