INS/GPS Integration: Global Observability Analysis

Observability is an important aspect of the state-estimation problem in the integration of the inertial navigation system (INS) and the Global Positioning System (GPS) as it determines the existence and nature of solutions. In most previous research, conservative observability concepts, e.g., local observability and linear observability, have extensively been used to locally characterize the estimability properties. In this paper, a novel approach that directly starts from the basic observability definition is used to investigate the global observability of the nonlinear INS/GPS system with consideration of the lever arm uncertainty. A sufficient condition for the global observability of the system is presented. Covariance simulations with an extended Kalman filter (EKF) and a field test are performed to confirm the theoretical results. The global observability analysis approach is not only straightforward and comprehensive but also provides us with new insights that were unreachable by conventional methods.