Observable degree analysis for inertial navigation in-flight alignment based on information theory

A method of analyzing the observable degree of time-varying linear systems as piece-wise constant systems(PWCS) is applied to the analysis of in-flight alignment(IFA) of inertial navigation systems(INS) whose estimability is known to be enhanced by maneuvers. It is shown that through the method based on mutual information, we can not only determine which state is observable and which is not, but also calculate the exact degree of observability of the system states. Simulation results demonstrate the validity of the method.