PASSIVE NAVIGATION USING INERTIAL NAVIGATION SENSORS AND MAPS

Marine inertial navigation systems are subject to a build-up of positi on, velocity, and attitude errors due to gyro and accelerometer errors , uncompensated vertical deflections of gravity, reference velocity er ror, and a host of other error sources. External references are common ly used to reduce or bound the navigation errors. Of the various refer ence techniques that are available to reduce navigation errors, passiv e reference devices/techniques are preferred. This paper describes one such technique that uses existing inertial platform accelerometers, I NS position and velocity data, and depth gauge information to measure the gravity anomaly profile. The gravity anomaly profile measurements are compared with a gravity anomaly map and navigation corrections are computed using map matching techniques in a passive navigation filter . The passive navigation filter models the inertial navigation errors, gravity anomaly map errors, and anomaly measurement errors to provide navigation corrections. The technique also uses gravity anomaly measu rements to improve velocity error. The anomaly map data is augmented b y anomaly measurements along the submarine track. Real time computatio ns using the Venning-Meinesz equations are performed to generate verti cal deflection corrections along the track. These corrections are then used to generate velocity corrections. The passive navigation techniq ue using gravity anomaly maps is totally passive. The test technique f or evaluation does not involve any changes to the existing operational ESGN hardware or software, however, additional software would be need ed to implement the passive navigation filter.