Computers: Custom maps made to order: Ordnance Survey is charting a new course. Max Glaskin reports

MAPS HAVE two big drawbacks. They are out of date almost as soon as they are printed and the area in which you are interested can be on the edges of several sheets.

These problems are eliminated by Ordnance Survey's Superplan, a network of computers in 15 British map shops linked, through telephone lines, to the Survey's central computer. They produce customised maps in minutes.

Superplan makes it possible to have a map of an area surveyed as recently as three days ago and to make it the centre of the map. The scale, shape and detail of a map can be tailored to meet specific needs.

According to David Rhind, director general of Ordnance Survey: 'No other national mapping organisation offers such a facility. They are all still bogged down in the bulk printing era.'

Superplan has three components. At its heart is the Ordnance Survey large- scale database which will hold 230,000 map files covering the whole of the country by the time digitising is completed in April 1995.

It is kept up to date by the second component, 701 surveyors, who record the changes on the ground and send in hundreds of digitised map amendments every day. The third component is the Superplan stations set up in the map shops.

Each Superplan national agent has a Sun Sparcstation 2, a powerful desktop workstation computer, with two 1.3 gigabyte hard disks containing all the data from the most popular 22,000 large-scale map files. The information is processed by a 424-megabyte hard disk and 32 megabytes of ram.

It has a 19-inch colour monitor, a mouse, a modem and a Hewlett-Packard DesignJet 600 monochrome inkjet printer which can plot maps up to 80cm wide and 300cm long.

The customer has immediate access to any of the files held on hard disk and others can be sent down the line from Southampton in 15 minutes, compressed into 100 kilobytes. The map on screen is customised with the mouse or keyboard. The map can be centred on the area of interest and information such as street names can be enlarged, reduced, highlighted or removed entirely. Mapping can be plotted at any scale from 1:200 to 1:5000 and the shape can also be decided - anything from a long rectangular map for a pipeline route, to an A4 extract for a single planning transaction.

Circular maps of quarter-mile and half-mile radius are also possible.

The price, which is higher than the old bulk-printed sheets, depends on the area covered and the degree of customisation and is constantly shown on screen in the main menu. An A4 site-centred urban map at 1:1250 is pounds 40 compared to pounds 18 for the old sheets, whose borders were locked to the National Grid. In spite of this apparent increase customers are happy.

Berkeley Homes Surrey, a property developer in Weybridge, spends pounds 200 a week on large-scale OS maps and Chris Larkin, in charge of planning, expects his map costs to rise by 20 per cent using Superplan. 'But this will be balanced by the convenience of having the site in which we are interested at the centre of the map and at the scale we need,' he said. 'Up to now, when a site has been at the edges, we have had to buy two or three maps, cut them up, stick them together and enlarge them on the photocopier. The big issue for us is speed; we can win or lose a development site in a couple of hours.'

Accuracy is also important to developers. Each night, when the Superplan retailer is closed, the database computer in Southampton relays the amendments it has received from the surveyors down the telephone line to the shop terminals.

On average it totals 200 changes, maybe on a few map files, but more likely spread over scores of files. It also adds completely new map files to the hard disks. This continual updating is crucial to Ordnance Survey, which must cover all its costs within four years. Until Superplan was launched last October a large-scale map was usually only reprinted every 40 years or when a large number of survey changes had been made. The Survey could afford a reputation for producing cartographic works of art, published on quality chart paper.

But Julian Cooper, product manager for Superplan, said: . 'For the most users, cartographic excellence is of little use if the map no longer accurately portrays the actual roads, buildings and other features that exist at the time the map is being studied.'

The demand for large-scale maps has increased dramatically in the last 15 years as property developers, utility companies and planning authorities struggle to keep pace with change. Julian Cooper expects Superplan to evolve, particularly as hardware such as colour printers become cheaper. 'We want to move to a Windows interface in the next two years,' he said.

With Superplan map sales running at 10 per cent higher than predicted, Ordnance Survey is making the most of boom in the demand for detailed geographical information.