A series of tiled models of superficial thickness covering the UK. The models are derived by direct modelling (natural neighbour interpolation) of BGS borehole records and BGS DiGMapGB-50. For the purposes of modelling, superficial deposits include sediments deposited during the Quaternary, subsequent Holocene rivers and coastal systems and also modern anthropogenic material, i.e. deposits that are less than 2.6 million years old. The 50 m x 50 m grids are overprinted with a minimum value so that areas where no bore data is present, but drift is known to occur, are given a minimum 1.5 m thickness. The superficial thickness models have been created as baseline datasets for the BGS Geohazard programme. They represent the first attempt by BGS to create nationwide models of such data and the models provide only a simple, mathematical interpretation of reality. The complexity of superficial deposits in Great Britain is such that it is only possible to model indicative values of thickness and elevation. The models should never be used as a substitute for thorough site investigation. The SDTM comprises three individual datasets; two datasets describe thickness variation and a third dataset details 'proximity' of the modelled data to the original source information. 1. The ASTM (Advanced Superficial Thickness Model) is a model of thickness variation indirectly derived from archive borehole records and map data. 2. The BSTM (Basic Superficial Thickness Model) is a model of thickness variation directly derived from archive borehole records. 3. The DBUFF (distance buffer) dataset is a calculation of spatial distance to the location of any data point used in the model. This provides the user with an indication as to how far the computer has had to interpolate and extrapolate the data from a measured observation point. For more information, refer to the user guide: The National Superficial Deposit Thickness Model (version 5). BGS Open Report OR/09/49. https://webapps.bgs.ac.uk/data/publications/publication.html?id=19867430
