Enhancement of GPS/INS Navigation System Observability Using a Triaxial Magnetometer

Enhancing the observability of an integrated navigation system (i.e., triaxial-magnetometer-aided global positioning system (GPS) and inertial navigation system (INS)) is analyzed utilizing the Earth-centered-Earth-fixed (ECEF) coordinate system. The error states of the extended Kalman filter (EKF)-based GPS/INS integration algorithm are not fully observable given the position and velocity measurements of a single-antenna GPS receiver. Although the manner of maneuvering a vehicle can improve observability, full observability is not guaranteed. Measurements of a triaxial magnetometer provide attitude information and can enhance observability of the GPS/INS system. In this study, enhancing observability through aid of a triaxial magnetometer is investigated applying an analytic approach. The results of the analysis show that using a triaxial magnetometer allows the error states to be fully observable when the vehicle performs maneuvers. In addition, only one unobservable mode exists, even if the vehicle is in a static or non-accelerating condition.