With the increasing use of Global Positioning Systems (GPS) and locations services, the need for maps - seriously accurate maps - has grown, finds Dan Simmons.
Satellite navigation systems flew out of shops last year, and the market continues to grow as drivers seek to keep one turn ahead of the crowd.
Maps are becoming more and more accurate, thanks to GPS
Sat Nav works when it can get a signal from at least three of the 24 US-owned GPS satellites orbiting the Earth. By cross-referencing the signals, most consumer GPS devices are accurate to within about 10 metres.
Europe launched the first of 30 new satellites last December, as part of the Galileo system, which promises accuracy to within one metre.
But knowing where on Earth you are is different from knowing what is around you.
One of mapping's new industry leaders is the US-based firm Navteq. In its London offices, around a dozen of its 500 drivers worldwide have carved up the south-east of England between them.
Points of interest are becoming more significant and need to be regularly updated. As contact numbers are added the map becomes a local directory.
Galileo will allow Sat Nav to operate inside of buildings too, so this work is becoming more important.
And this year Navteq started allowing certain businesses to buy their way onto the maps listings.
Click followed Dan Childs, a team leader from Navteq, on his way to a new housing estate he had spotted to the north of London, in Watford.
The car was equipped with a digital camera which records to a laptop what the driver sees, and this was connected to the car's specialist GPS receiver.
He used a games console controller to "drop" voice notes of any changes he sees onto the recorded journey. He will not update the map unless he has seen something for himself.
As many as a third of all the updates to the map are made after changes are spotted, by chance, on the way to somewhere else.
GALILEO UNDER CONSTRUCTION
A European Commission and European Space Agency project
30 satellites to be launched in batches by end of 2010
Will work alongside US GPS and Russian Glonass systems
Promises real-time positioning down to less than a metre
Guaranteed under all but most extreme circumstances
Suitable for safety-critical roles where lives depend on service
When Dan and driver Graham finally reached the estate, the boys were literally trailblazing at 10 miles per hour.
Coloured arrows registered their direction and position every few seconds, slowly mapping out every metre of the new road.
Dan said: "Even if it's signed as a cul-de-sac we drive all the way to the end of the road and do a U-turn; we do lots of those each day.
"We want to GPS it from all directions and get all the names correct. Then when we get back to the office I can add it all into the database."
With each twist and turn of every road being mapped out by an individual person it can take quite a long time before those changes make it to your GPS system.
Adrian Little, Navteq's UK Marketing Director, told Click: "We update our database daily, and release it to the people who make GPS systems and devices on a quarterly basis.
"At that point it is up to that manufacturer when they will release new map data to their consumers and drivers for use in their everyday lives.
"The time it takes from us seeing that change to the change being present in the vehicle can vary from as little as six months to perhaps as much as 12 to 18 months."
Back in the office Dan not only updates the map but can add his own notes to help device manufacturers determine the best routes and voice instructions for the driver.
For instance, Dan considered one turn, though legal, to be too sharp to expect a driver to make. As a result, most Sat Nav manufacturers will not direct their drivers to take it.
Dan added: "We hope that in future, as well as downloading information from us, drivers will be able to upload information to us, so that we can be made aware of any changes to a road network almost instantly."
In the meantime, Navteq would like people to e-mail them if the maps are wrong, because keeping an up-to-date record of the world around us is turning out to be an even bigger task than finding exactly where we are.