The enhancement of INS alignment using GPS measurements

The integrated GPS/INS system has been adopted in many navigation systems for its synergistic results. As an application of the GPS/INS integration, the alignments of strap-down INS (SDINS) utilizing GPS carrier phase and differential phase rate measurements are introduced. An observation model of double-differenced GPS carrier phase and differential phase rate measurements is newly derived in order to be used with the SDINS alignment process. The performance of the INS/GPS combined system is analyzed through covariance analysis. Consequently, the covariance analysis results confirm that all states of the differential phase rate measurements combined system can be estimated more efficiently than that of the only carrier phase combined system even in case of 1 baseline and 4 visible satellites