an old friend of mine drove a truck for a company that had installed GPS satellite tracking.
i told him "for some fun" cover the dome with aluminium foil, move the truck and wait for a call.
he drove from his house to downtown, just a couple of miles, and removed it.
his phone rang and the dispatcher asked "how fast are you going? the speed of light"?
i never found the exact figure, but i did like the question.