Thanks ... although I'm not so sure. In my case, The NAV computer knew the car was moving and changing direction, however didn't know where it was in space relative to anything else. Unless I'm not mistaken the wheel sensor can determine if the vehicle is moving, and the gyro inside the nav computer can determine if the vehicle changed direction .. but thats it.

And even when it did get the GPS signal again from 3 or more satellites to determine its location, it had a melt down and rebooted