From Expanding Earth, the latest from xkcd‘s What If? section:

After the initial jolt, one of the first effects you’d notice would be that your GPS would stop working. The satellites would stay in roughly the same orbits, but the delicate timing that the GPS system is based on would be completely ruined within hours. GPS timing is incredibly precise; of all the problems in engineering, it’s one of the only ones in which engineers have been forced to include both special and general relativity in their calculations. (emphasis added)

And I use it to find tupperware in the woods.

Science. It’s pretty amazing, and damn near magic.