Enhanced estimation of position aided INS utilizing trajectory history

The inertial navigation systems (INS) solution drifts in time due errors exhibit by their inertial sensors (gyroscopes and accelerometers). Therefore, INS are aided by external measurements. Fusion of INS with external sensors enables the estimation of most INS states depending on the aiding sensor type and platform dynamics. In particular, for any platform travelling in a straight and levelled trajectory with position updates, the heading angle and some of the inertial sensors error states are not observable. In this paper, we propose a method to extract attitude information directly from the history of position measurements provided from the external aiding sensor. Utilizing simultaneously the attitude information and position updates in the navigation filter enables the estimation of the heading angle as well as the inertial sensors error states. That is, using the proposed approach the system becomes completely observable. Simulation results are provided to show the improved performance when applying the proposed approach.