AROUND 400 million features of the British landscape on a revolutionary digital map show the whole country redrawn in unprecedented detail.

Southampton-based national mapping agency Ordnance Survey has taken the wraps off OS MasterMap after a two-year project to digitally reference not just every building and field, but detail as fine as railway signal lights and free-standing letter boxes.

It is like an enormous national jigsaw made up of 400 million pieces, with each one 'barcoded' with an unique 16-digit reference number known as a topographic identifier or Toid. The Tower of London, for example, is 0001000006032892.

Toids offer a higher level of detail than postcodes or individual addresses as they identify millions of non-addressable properties and natural landscape features such as small waterways and areas of woodland.

As well as telling you where a feature is, a Toid is also a direct link to a description of what it is. Best of all, a Toid can be loaded with extra detail within a user's computer system and shared between users, so acting as an unambiguous and electronically mobile package of information.

This breakthrough opens up a host of possibilities in easier data sharing and management for utilities, local and central government, and any business supporting a branch network, customer base, or other geographic infrastructure. The associations created by Toids could even foster closer cooperation between government and business.

"OS MasterMap is the most detailed, definitive and intelligent mapping we have ever produced," says Vanessa Lawrence, Ordnance Survey's director general and chief executive. "It has been developed in consultation with industry and government and with the knowledge that around 80 per cent of all the information held in Britain has some geographic content. As they are taken up, Toids will become common hooks held on any number of databases within and between organisations, bringing significant benefits in the way information is integrated, manipulated, analysed and presented."

Unlike earlier very detailed digital map data, OS MasterMap provides continuous mapping of the whole of Britain from which users can select the precise area of coverage they need. As it is not restricted by fixed map tiles, it is truly seamless. It has also been created in a series of themed layers which users can pick and mix as they wish. Nine themes become available in the initial release of data today: roads, tracks and paths; buildings; land; rail; heritage; height; water; structures; and boundaries.

Users can stay up to date through regular web updates showing only those features that have changed. Whereas before they would have received a complete resupply of their data on CD-ROM, the change-only facility means they can be sent just those features that have been updated, cutting dramatically the size of update files and the overall costs of data handling. In time, all Ordnance Survey products will be created from OS MasterMap - even new generations of its most popular papermaps such as Landranger and Explorer.

Consultations are under way with users of the existing large-scale digital product, Land-Line, to ensure that the conversion to OS MasterMap is as easy as possible. In the meantime, the two will run in parallel.