Zone Design for Planning and Policy Analysis

The geographical information systems (GIS) revolution, the widespread availability of digital map data and the ability to attach accurate locational references to address databases via Address Point and the Postal Address File creates the possibility of users designing their own customised zoning systems in the UK. For the first time, it is possible to take control of the zones required for reporting, mapping and analysing spatial information. This situation is, of course, not entirely novel. Ever since the first point in polygon algorithms were used in the early 1970s and digitisers permitted polygons to be encoded as strings of x, y coordinates, some users have had this ability to restructure their spatial data. Similarly, the hierarchical nature of census enumeration district codes (and postcodes) provided easy ways of performing hierarchical spatial aggregation; data for electoral or census wards could be aggregated to districts, counties or local education areas and data for unit postcodes aggregated to sectors et cetera Indeed, the BBC Doomsday system developed in the mid 1980s offered 24 different standard geographies (Openshaw et al. 1986). Whilst this was useful, the degree of aggregational freedom was still restricted by the need for the spatial building blocks to nest within the target output geography and the user had to know which aggregation was required. In practice, this meant that you were forced to restrict zone changes to one or other of the standard set of geographical areal definitions.