Long before ships relied on GPS to ... before radio navigation systems such as LORAN, vessels relied on a still impressively sophisticated means of determining their position: inertial navigation.

Underwater gravity-aided inertial navigation systems (INS ... to improve the accuracy of positioning systems, particularly in environments where GPS signals may be weak or unavailable.

Inertial Navigation Systems ... in applications such as stationary and GPS-aided in-motion alignment[3]. Furthermore, integrating INS with Global Navigation Satellite Systems (GNSS) has been ...