A submarine navigator for the 21/sup st/ century

Recent advances in technology on multiple fronts will enable new and improved approaches to precision navigation of submarines. Improvements in interferometric fiber optic gyro (IFOG) technology have made it possible to use IFOGs in a high accuracy navigator. The use of spherical gimbals for improved temperature control and inertial instrument error autocompensation has been made practical by computer-controlled machining. The use of sonar in certain covert situations will become more prevalent, facilitated by lower power sonar systems and advances in signal processing technology. Satellite based altimetry will make it possible to compensate for gravity deflections using lookup tables. Satellite altimetry will also allow us to make tables of gravity anomaly and ocean depth available to the overall navigation process. Using these advances, it is possible to use measured gravity anomaly from the ship's IMU and sonar soundings from its sonar array to estimate and correct navigation position errors. A navigator is currently being developed at Boeing that will incorporate these new developments as well as the traditional velocity log, pressure depth meter, and Global Positioning System aiding. The new inertial navigator outputs, as well as the set of currently available navigational aid outputs, are combined in a series of filters that allow for the detection and removal of transient errors to furnish the best available position, velocity and attitude to the ship's systems.