postcode

A UK postcode covers around fourteen different addresses. Postcode polygons are areal units based not on enumeration districts or wards, but on aggregations of postcode divisions. Unit postcode boundaries are generated by the creation of Thiessen polygons around individual address locations, and the merging of adjacent polygons with the same postcode. These are too small to be used by geographers because of confidentiality constraints, but are aggregated to form output areas. (S. Openshaw (ed.), Census user's Handbook, 1995.)