GB Profiles91 provided the facility to retrieve details on the general residential characterisitics of the areas represented by every unit postcode in Great Britain. A short description or 'pen-picture' of the type of residential area associated with the ED containing the postcode was also provided. The system contained two classifications with 10 and 100 clusters, created using a set of algorithms widely used in the geodemographics industry referred to as the Census Classification Programs (CCP).
However since then, Stan Openshaw has constructed more than 100 different census data classifications with different methods and at varying resolutions including a recent customised classification, which is now included in the lastest version of the SAR data. The Leeds Geodemographic Analysis System (LGAS) is intended as a way of providing wider access to this broad range of classifications as well as offering better reports of the results and greater input and output flexibility. The new system will work with either postcoded data or 1991 ED codes.
Development of the Leeds GAS was sponsored by the School of Geography at Leeds University and developed jointly by Linda See and Stan Openshaw in 1999. The system is in theory portable (it uses a web browser as an interface) but currently requires access to the Sun Solaris UNIX operating system.
The design of the system is quite straightforward: there is a CGI-based graphical user interface which communicates with software that reads the chosen classification files and processes the user data.
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