[Myrddin]

The technology being created for 911 is slated to be exploited commercially by companies offering geographically sensitive information services. The LAT/LON associated with your phone will be used to direct you to the closest McDonalds, gas station, hospital...if you can think of a business that would be willing to pay to have a service route customers that are nearby...that is the payoff. The TDOA stuff ranges in accuracy from 80 to 150 meters. It isn't nearly as good as having a real GPS onboard. That is why OnStar and Wingcast put a top quality GPS into their in-car electronics package. The GPS fix is good enough to tell the service agent what side of the street, which direction and your nominal speed (if appropriate). Airbiquity makes a "backpack" GPS that fits on some cellphones like an extra battery. GPS and E911 work great on open road with lots of sky and few obstruction to block signals. Both technologies fail miserably in an environment with tall buildings that obstruct the sky and the path to the cell towers.

[Travis McGee]

Thanks for the info. The commercial implications alone could be vast!

Pablo Escobar's trackers experienced the same frustrations trying to track him in large cities: they would end up tracking ghosts and reflections and multiple readings.