Inertial navigation systems[1] have been used for more years than GPS has existed. Even now almost all military drones / rockets / ICBMs use very precise inerti

Inertial navigation systems[1] have been used for more years than GPS has existed. Even now almost all military drones / rockets / ICBMs use very precise inertial systems. [1] http://en.wikipedia.org/wiki/Inertial_navigation_system http://en.wikipedia.org/wiki/Inertial_navigation_system