Scottish Settlements Urban and Rural Areas in Scotland

Annex C - The Methodology for 2000

Why use postcodes?

2. There is merit in using a definition of urban that can be implemented automatically. The resulting settlements can be identified and updated inexpensively. Using postcodes offers such an approach. National Records of Scotland (NRS) holds information on the number of addresses contained by each postcode, and its boundary from which the area, and hence the density of addresses, can be calculated (as addresses per hectare). This information can be used to derive a selection of urban postcodes that will make up a settlement. The disadvantage of an automatic method is that there is limited scope for human intervention to compensate for any anomalies that may arise in the input data that was created for other purposes. Such anomalies may exist because of how:

• Royal Mail (RM) group addresses into postcodes;

• RM distinguish large users (LU) and small user (SU) postcodes; only SU postcodes are given boundaries by NRS; LU postcodes are instead 'linked' to the SU postcode whose boundary contains the LU; or

• NRS draw the boundary of SU postcodes; in particular, how unpopulated land is included within the boundary of any postcode (the NRS Census requirement is that postcodes should cover the entire land mass of Scotland); or because

• the information on addresses and postcodes provided by RM is not fully up to date; or

• the information NRS use to distinguish residential from non-residential addresses is not fully accurate.

3. On the third of these points, we realised some time ago that the delineation of the boundaries of settlements would be affected by how we had drawn the boundaries of postcodes lying near the edge of a town or village. A postcode may contain a development consisting of tens of dwellings but fall below the density threshold because the boundary includes a large tract of unpopulated land. Work to identify such postcodes near the boundary of 1991 localities and, where possible, amend the boundary of the postcode is now complete. We are examining ways of systematically building this task into our general work of maintaining postcode boundaries.

4. NRS believe that these elements of subjectivity are outweighed by the advantages of an automatic method of identifying urban Scotland. Being automatic, the method is inexpensive, and can be repeated relatively frequently (annually to begin with) to keep it up to date, thereby helping to address some of the anomalies mentioned above. We are confident that in the main this method is fit for the various purposes to which the results will be put.