As the blue Renault Scenic rolls into Alec Rolph Close, on a nondescript new housing estate on the outskirts of Cambridge, a postman and a couple of locals turn to stare. This isn't because the car itself is anything special, but on the roof is a chunky white antenna which signals that something unusual is going on here - possibly something official and very probably unwelcome.
In the passenger seat of the car, a man is hunched over a laptop muttering things like "house numbers one to five, no buildings to the right" into the microphone of a PC headset. All around him are wires and flashing LEDs. A digital video camera is fitted to the windscreen, recording the road ahead as the driver slowly steers the vehicle around every section of the close - even into the dead ends.
If you see such activity in a street near you, fear not. It is an intelligence operation of sorts, but it is not the work of a covert, military or malign agency. The giveaway is the slogan painted on the front doors of the car: "Navteq On Board".
Navteq, a US-based firm that has had a British division since 1994, is a global leader in the production of digital maps used in satellite navigation systems, internet maps (like those provided by Google and Yahoo!), and online route finders like Microsoft's AutoRoute. If you've ever used any of these products to get from A to B, the map data probably came from either Navteq or its Belgium-based rival Tele Atlas, which it is currently battling for global supremacy in the digital-mapping business.
Surprisingly, given the leading-edge nature of satellite imagery, the collection of raw map data involves driving the length and breadth of a country's road system, from motorways to cul-de-sacs, and revisiting them when anything changes. This is why Navteq was at Alec Rolph Close. After overlaying postcode data from Royal Mail on to a database, Navteq's analysts noticed the close was missing from their maps. So they sent out Dan Childs, geographical analyst and team leader, along with a hired driver, to put it on the map.
Many travellers today can't live without digital guidance. New research by the RAC reveals that half of young drivers can't read paper maps. Sixty-five per cent of motorists aged between 18 and 35 didn't know that "A" roads were marked in red on road maps, and 29 per cent mistook the M40 for the River Avon; 20 per cent had never used a road map, while 26 per cent didn't have one in their vehicle. But half of motorists depend on online route planners. Among the under-35s, this figure rises to 61 per cent, while 26 per cent of that group now rely on sat nav to plan their route.
Today, Navteq's car is packed with hi-tech equipment. "All our tools and devices just slot in, so we can use any vehicle," said Childs. "The GPS receiver and laptop run off the cigarette lighter and the GPS antenna is fixed to the top of the car by a strong magnet - we just wedge the connection wire through one of the back doors."
Wearing a PC headset, Childs records voice notes of the 10mph journey around this tiny close. "I never update the map unless I've seen something for myself," he says, looking at a black screen with lines and squiggles denoting roads and other landmarks. A green arrow marks the car's progress, tracked by DGPS (differential global positioning system), a sophisticated system accurate to within one metre - regular GPS is accurate to around five metres. The car literally sketches out the road.
When Navteq began its UK operation over a decade ago it had to record every navigable section of road from scratch. But why didn't it just use existing printed maps? "Digital maps are essentially different from conventional maps, which are viewed from an aerial perspective," Childs explained. "For navigation you need the horizontal perspective - the view through the driver's eyes. By checking what a section of road will look like to the driver, you can sort out whether the navigation instructions need to say turn left, keep left or fork left, or maybe nothing if it is obvious where the road carries on."
The race for market domination has inspired Navteq and Tele Atlas to add ever greater levels of detail to their maps. Speed bumps, speed limits and speed cameras are now plotted, and even separate lanes at roundabouts. Navteq is now also including information from Thomson Local directories, so your sat nav system can take you, via the best possible route, to the nearest Woolworths.
But if satellite navigation is so accurate, why have drivers been guided into the River Avon or along precarious cliff edges? "The cliff edge incident was a mapping error and was immediately rectified," explains Jennifer Fondrevay, marketing communications director at Navteq. "But it is worth noting that in this instance drivers would have had to have been very determined to get to the cliff edge as the route was gated." She also points out that errors can be down to the software, not the maps themselves. And besides, she adds: "Millions of successful journeys are made using sat nav systems - in 2005, in Europe alone, around four million routes were calculated each day using in-vehicle and portable systems."
Four times a year, Navteq releases the findings from 600 patrols like this one in countries around the world. It's then up to the sat nav manufacturers to get the updated maps to you - it can take up to 18 months.
And if you thought the job of digitally mapping the world's roads could be less than exciting, think again. Childs recalls how he thought he was going to be shot inSouth Africa a few years back. "I was mapping an area around Durban when the local driver I was using nearly crashed us into a military patrol," he said. "One of the soldiers jammed a sub-machine gun through my window and I thought my number was up - until he said: 'Are you guys lost?' "
Streets ahead: the best navigation gadgets
* Garmin Nuvi 350
Sat nav mapping, restaurant information and MP3 player all in one. Also receives up-to-date traffic information via extra optional receiver. £291.96 from www.blokestuff.com
* TomTom GO 910
Easy to take from car to car, with a 10cm LCD anti-glare screen that adjusts to changing light conditions. Includes US and European maps, MP3 player and hands-free Bluetooth phone function. £389.79 from www.amazon.co.uk
* Sony NVX-P1
Comes with maps of all of Western Europe except Greece, easy to transfer from vehicle to vehicle. £349.99 from www.the hifistore.co.uk
* Medion GoPal PNA 515
Portable navigator with 9cm colour touch screen and integrated traffic warnings receiver. Maps cover 31 European counties, with tourist attractions etc. £199 from www.routeplanners.co.uk
* Nokia N95 Smartphone
The first N-series phone with integrated GPS. As well as all the latest mobile technology, including high-speed connectivity, it comes with maps for over 100 countries and details of 15 million points of interest. Price tba. Pre-order from www.expansys.comReuse content