Ordnance Survey: Putting GIS on the map

The surface of the Earth is, with one exception, one of the lesser-mapped places in the solar system. Both Venus and our own moon have famously been mapped more exhaustively than our own planet. The one place on the Earth that has been well mapped is Great Britain, thanks mainly to the paranoia of an 18th century government that wanted to plan adequate defences to repel invasions.

It is inconceivable that the people who began the job in 1791 could have any idea that, over two centuries later, the work would still be continuing. In fact, what began in 1791 as a finite job mapping the south coast of England to help plan defences against invasion, today spans the whole of England, Scotland and Wales, with over £100bn of commerce depending on it. Geographical data finds its way into some aspect of pretty much every company in the UK: Ordnance Survey, which today continues the job it started when it was the board of Ordnance -- the defence ministry of the day -- in 1791, believes that some 80 percent of all information includes some geographical element.

"Tesco uses geographical information to figure out not just where to put stores, but how to stock them," says Ordnance Survey marketing manager Neil Wilkins. "They need to know how to stock various stores depending on the local demographics."

Mapping the country to support such data is a job that will never finish. The current workforce at Ordnance Survey dedicated to mapping comprises more than 400 surveyors, who constantly measure and record the changing British landscape from a network of offices stretching from Inverness to Truro.

Information gathered by the ground staff is supplemented by an intensive programme of aerial photography, particularly in rural areas, resulting in about 5,000 changes being made every day to the MasterMap: to date there are some 400 million individual features.

Up until the 1970s, these maps were all paper-based: that meant a library of 230,000 sheets of paper, or tiles. Obviously, as the demand for mapping data increased, this situation proved increasingly inadequate, and so Ordnance Survey began a programme of computerisation. Even that job took almost a quarter of a century, and was not completed until 1995. But the effort was felt to be worthwhile: today, it means that extracts of the latest edition, which contains some 400 million features, can be accessed instantly by the public through a national network of computer-linked retail outlets in the Ordnance Survey Options network.