Long before GPS, sailors navigated by the stars. While being able to determine your position based on the stars is still a useful skill on the open ocean, it’s a lot less time-consuming to let a computer do it for you. That logic is part of why the Navy stopped teaching celestial navigation around 1998, choosing instead to focus on the ubiquitous electronic navigation systems that cadets would encounter far more often in the service. Now, NPR reports, celestial navigation is being reintroduced into the course loads of Annapolis cadets.

The Navy is beginning to teach celestial navigation again in order to reduce its dependence on GPS, which is not infallible, according to NPR. While stars are not the most accurate way to determine a ship’s course—a sextant is only accurate to a 3-mile radius—it is reliable. If satellites are shot down or hacked or out of range, Naval officers still need to be able to find their way. The military is also wary of placing too much trust in electronic navigation when people can easily buy GPS jammers over the Internet (though the devices are illegal in the U.S.).

And so service men and women are being taught the absolute basics, going back to using the planets and stars and a sextant to find direction through a long series of mathematical calculations. Before the course was canceled in the 1990s, celestial navigation was an unpopular, tedious class at the Naval Academy, and many midshipmen were happy to banish it. But should they encounter a GPS jammer in the future, today's students will probably be more than happy they know what to do with a sextant.

[h/t NPR]