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Data update

It is becoming increasingly easy to obtain digital maps and photographs on disc and by e-mail, says Lisa Russell.

Asked to think of a map 10 years ago, you would picture a piece of paper. Today, a floppy disc, CD or even an e-mail are more likely to spring to mind.

Use of digital maps and the digitised aerial photographs on which it they are based is escalating. Dozens of firms are also finding more and more niches in the rapid provision of extra information linked to the maps.

Today, 70% of Ordnance Survey customers receive their information in electronic form. The figure is even more dramatic in the local authority sector, where the 1990 split of 90% paper and 10% electronic has been reversed.

Two of the latest companies to offer new services are GeoInformation Group, with an update to its colour photographic database of London, and Ordnance Survey's new trials of map supply by


GeoInformation Group's London Revealed is a photographic database of the entire area within the M25. An update is just being finalised, with some areas already available and the full picture due out early in 1999. The firm flew across the entire area this summer, despite the bad weather. By 'mosaicing' scans of the negatives together, a seamless image is produced. Digital photography is not yet feasible because typical 40Mb file sizes are too large for today's digital cameras.

Among uses of the system are planning, site selection, mapping and asset management. Current users include over half the London boroughs, government departments, engineers, utilities and architects. The pictures are equivalent to a viewing scale of 1:1,000 providing sharp images of objects as small as 250mm. Lower resolution pictures are also available, as is a database of building outlines, heights and roads. London Revealed is part of a series of images covering 75 urban areas in the UK, as well as places elsewhere in the world.

Anything available from Ordnance Survey can be delivered electronically in one form or another. Over half of the agency's 38 agents around the country have recently started a major trial, sending the computerised Superplan Data maps out to customers by e-mail. Superplan Data is very detailed, showing even the shapes of individual buildings and the locations of private garages. A starter pack ensures the customer's computer is set up to handle the data, then orders can be placed and the data sent as an e-mail attachment. The customer chooses the map's centre point, and the files are in CAD compatible DXF format.

Paper maps are rarely updated more often than once a year, and some new editions can appear as irregularly as once every five years, but the underlying databases and hence the digital maps could be modified on a daily basis. OS has a team of 550 surveyors on the ground, plus aircraft teams and interpreters. Thousands of pieces of information are fed in every night, so that people ordering a digital map get the very latest survey. Resolutions of commercially available satellite photography are not yet sharp enough for OS's needs, but a team is working on the development.

A increasingly wide network of value added resellers takes OS

data as a starting point. The 50 or so firms augment the information, with new ideas being developed every week. Products supplied this way are as diverse as Microsoft's Autoroute Express journey planner, Infrasoft's OSMOSS 3D mapping, Building Research Establishment's wind-over-hills consultancy and Aerofilm's digital, orthophotographs - rectified aerial images supplied to individual sites.

Intergraph's GeoMedia software uses an open data format allowing different sets of information - not only from OS - to be viewed in the same session.

Another value added reseller is Landmark Information Group which has at its system core the OS large scale digital map of mainland Great Britain. This is linked to a relational database, holding environmental information.

'When a civil engineering consultant like WS Atkins is going on to a site, we can print out a map centred on the area of interest,' explains Landmark chairman Christopher Roper. Other information like the location of sites of special scientific interest or British Geological Survey's borehole logs can be linked in, as can information about discharge consents and known hazardous substances. 'They can get a clear picture of what is on the site.'

Exeter-based Landmark was formed in spring 1995, and has been delivering reports since September that year with the process becoming increasingly automated as the pounds6M investment has come online.

An ongoing task is to extract and digitise details of quarries, gas and chemical works from maps going back to 1850, enabling Landmark to build up 'a complete database of the nastier features you are likely to encounter', says Roper. Another feature of Landmark's system is that it holds all the historic OS maps back to 1850. These were originally drawn to varying scales and projections but can be site centred. This allows someone to check perhaps eight or 10 maps over the years, tracing the lives of buildings, quarries or canal basins and helping pinpoint sources of past contamination. A recent coup was in providing the mapping for the Time Team archaeological investigation programme on Channel 4.

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