Defining & Delineating the . . .

The increasing availability of very high spatial resolution data using the unit post code as its geo-reference is making possible new kinds of urban analysis and modelling. However, at this resolution the granularity of the data used to represent urban functions makes it difficult to apply traditional analytical and modelling methods. An alternative suggested here is to use kernel density estimation to transform these data from point or area 'objects' into continuous surfaces of spatial densities. The use of this transformation is illustrated by a study in which we attempt to develop a robust, generally applicable methodology for identifying the central areas of UK towns for the purpose of statistical reporting and comparison. Continuous density transformations from unit post code data relating to a series of indicators of town centredness created using ArcView are normalised and then summed to give a composite 'Index of Town Centredness'. Selection of key contours on these index surfaces enables town centres to be delineated. The work results from a study on behalf of DETR.