Most devices don’t have one, according to Andrew Johnston, curator of the new Air and Space Museum exhibit, “Time and Navigation.” He believes that will have to change considering that “GPS is shockingly easy to interfere with”:
One of the famous examples was at Newark Airport. The FAA was experimenting with a positioning system there and every so often, the GPS would stop working briefly. It kept happening over and over again. They finally figured out that what was going on was that right next to the airport was the New Jersey turnpike and the trucks were driving by with GPS jammers. And they’re inexpensive. You plug it into the cigarette lighter power adapter and GPS doesn’t work for the vehicle. The problem is that the zone that it affects is much bigger than a truck. The signal bleeds out, in this case, into the grounds of the airport.
(“The Astronaut Who Captured a Satellite” from NASA)