Passive Inertial Navigation of Maritime Vessels Using a Gravimeter

A novel filter design is shown that combines a traditional inertial measurement unit (IMU) with a gravimeter and advanced algorithms for passive navigation of surface and sub-sea maritime vessels (i.e., non-emanating and free of external signals like GPS). Unlike prior filter formulations, the newly derived filter provides physically frame-consistent estimates while exhibiting faster convergence than common linearized filters, such as the standard extended Kalman filter. Specifically, a consider-based frame-consistent filter is derived that provides robustness to low observable states, including small IMU scale-factor errors and misalignments. Simulation studies show that the new filter is effective at providing good attitude and position estimates based solely on the passive sensing system. Actual sea trails of the new approach are shown with comparisons to a GPS-based filtered solution. These sea trials validate that the derived approach can provide excellent passive navigation for extended periods.