The Relative Utility of the Central Postcode Directory and Pinpoint Address Code in Applications of Geographical Information Systems

Abstract

Considerable use is made of postcoded data in GIS (geographical information system) research. This is especially true of applications in geodemographics and epidemiology, but the work described here is of relevance in any attempt to attach specific locational identifiers to unit postcodes in Britain. Conventionally, unit postcodes are given an explicit spatial reference by means of the Central Postcode Directory (CPD), in which 100-metre grid references are assigned to each postcode. However, in a major undertaking, the company Pinpoint Analysis Ltd is digitising every property, both domestic and commercial, in the country. This gives a 1 metre grid reference for each such property; from the set of all addresses in a unit postcode a centroid may be obtained. In this paper the locational referencing provided by the ‘Pinpoint Address Code’ is compared with that of the CPD. The empirical work draws on data for Camden in London, but reference is made to earlier work in Whitehaven. We make some observations on the value of using point data in GIS (notably epidemiological) research, rather than relying on data for essentially arbitrary areal units.