Observability of Geomagnetism/GPS/SINS integration during maneuvers

Observability of Geomagnetism/Global Positioning System/strapdown inertial navigation system (Geomagnetism/GPS/SINS) integrated system was analyzed during maneuvers. Instantaneous observability was adopted for the observability analysis of time-invariant and time-varying system. When there was no rotation relative to the Earth and the linear acceleration was constant, the system model became time-invariant. Observability analysis results show that there are at least one and at most two instantaneous unobservable states in the time-invariant Geomagnetism/GPS/SINS system, which are at least three in the time-invariant GPS/SINS system. The observability of time-varying system was analyzed for two types of maneuvers, nonconstant accelerating maneuvers and constant angular rate turn maneuvers. The sufficient conditions for instantaneous observability of system are presented for these two maneuvers. And the necessary condition for instantaneous observability is presented for nonconstant accelerating maneuvers. It is shown that the appropriate maneuver can enhance the instantaneous observability of system and all the states in Geomagnetism/GPS/SINS integrated system can be made instantaneous observable by appropriate maneuver.