Cruise Missiles Don’t Just Rely on GPS

Cruise missiles use GPS for navigation. As we have seen, GPS signals can be rather easily disrupted by an inexpensive jamming device. This would be a problem if cruise missiles didn’t have a backup, as Technology Review explains: terrain contour mapping or TERCOM, which uses preloaded contour maps and onboard radar. And if that doesn’t work? Dead reckoning. Via @gpstracklog.