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Last Updated: Thursday, 24 May 2007, 06:47 GMT 07:47 UK
Keeping an eye on the road
By Jonathan Fildes
Science and technology reporter, BBC News

On board the GPS van with Gudrun Vanlaar and Stijn Ulenaers
Stijn Ulenaers and his girlfriend Gudrun Vanlaar have been mistaken for spies, security guards and snoopers.

"Once somebody even thought we were crazy people trying to record everything about our holiday," says Miss Vanlaar.

The confusion tends to arise because of their unusual vehicle and what some people may describe as erratic driving habits.

The young Belgian couple are surveyors for Tele Atlas, one of several firms including competitor Navteq that produce digital maps for satellite navigation devices.

It is their job to drive a tangerine coloured camper van, armed with six CCTV cameras, a gyroscope and various other sensors, up, down and around the highways and byways of Europe to check the accuracy of the firm's digital maps.

"We have done about 180,000km so far," explains Mr Ulenaers, a trained criminologist who wanted a job that would allow him to travel.

Colossal task

As they drive, cameras connected to two computers inside their mobile home constantly record images from the front side and rear of their van.

Mr Ulenaers and Miss Vanlaar, Tele Atlas
The couple wanted a job that would allow them to travel

"It takes one week to fill a 250GB hard drive," says Miss Vanlaar, who is on a break after degrees in teaching and anthropology.

The images are sent to India, via the company's headquarters in Belgium, where they are used to verify that the maps already loaded on to devices are accurate and up to date.

In Delhi a team of 800 people watch the images and compare them to the existing maps.

"It's a never ending story," says Allan Rasmussen of Tele Atlas.

It is estimated that between 15 and 20% of the road network changes annually. That might be anything from a new road sign to an entire new motorway.

The maps are initially created from existing sources, such as the ordnance survey in the UK combined with aerial photography, information from the highways agency and local authorities.

"We use 50,000 sources of data worldwide," says Mr Rasmussen.

This colossal amount of information allows the company to pinpoint where things have changed and where to send one of their fleet of 22 mapping vans such as the one driven by Mr Ulenaers and Miss Vanlaar.

Summer job

"So far we've been to Spain, Portugal, France, Italy, Corsica, Denmark, Belgium, Russia and now Great Britain," says Mr Ulenaers.

Mapping van, Tele Atlas
The six cameras each take four pictures per second

Once there, the digital nomads follow a predefined route, one driving and one checking the quality of the images.

At the end of the day they pull the van into a campsite to check a snapshot of the images.

"If you can read the signs the images are good," says Miss Vanlaar.

But if more than 5% are unreadable the whole batch is scrapped and the couple have to follow the same route the next day.

Image quality tends to deteriorate towards dusk or if it is raining, which means that the vast majority of their work is done when the sun is out and shining.

"We might work 10 hour days in the summer," says Miss Vanlaar. "On a bad day we might work for just one hour."

As they drive the couple have to make sure they catch every detail.

"When we reach a roundabout we have to do a full circle so that the cameras see all of the exits," says Mr Ulenaers.

Combined, the company's drivers cover more than 3m km (1.9m miles) every year to keep the maps up to date; a job that Mr Rasmussen thinks will become more and more important.

"In a few years people will have cars that drive automatically and then you will have to rely on the accuracy of the maps 100%."

But until that day other more traditional forms of navigation will continue to be used, even by pairs of surveyors driving from country to country equipped with the latest hi-tech gadgetry.

"We just look at the atlas and take the highway - it's easy," says Mr Ulenaers.

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