While the electronic maps function on mobile phones is one of their big selling points, they can be expensive beasts to run abroad. Some testing by Garmin on an HTC phone on an O2 pay as you go contract showed that using mobile navigation on the 185 mile Calais to Paris trip cost £24 to £39 in roaming charges one way.
Roaming charges for pay as you go customers were £3 a MB and £2 a MB for customers on contracts.
On the same basis, navigating a trip from Calais to Cannes on a mobile contract would cost £298.80 for 747 miles, according to the Garmin press release. Garmin - the makers of in-car navigation devices - have an obvious vested interested in getting you to use their devices and maps rather than the one that comes bundled with your mobile phone.
But - it raises an interesting point: GPS location is free and works worldwide, (the little ping that mark your location get sent up to American satellites, and if you have a GPS device it doesn't matter whether you're in Tyneside or Timbuctoo) but downloading maps isn't. So, if the maps are already there then it's hunky-dory, but if they're not, then downloading that data is expensive.
Phones with maps already onboard - some Nokia and Android phones will not charge you for navigating abroad.
One more reason to wish mobile networks would get their damn roaming charges sorted out..