If you live in the southeastern part of the United States and you depend heavily on your GPS, you may want to have some kind of a back up plan.
According to a notice from the Federal Aviation Administration:
It'll be something to keep in mind if you rely on your GPS for navigation. Just be mindful of where you're going when your GPS instructs you to make a right turn. And for those of you on foot, there's nothing wrong with the plain old map and a compass.