Transfer Alignment using an Integrated INS/GPS as the Reference

Dr Paul D. Groves

Abstract:	The accuracy of the transfer alignment of a missile inertial navigation system can potentially be enhanced by using an integrated INS/GPS navigation system on board the aircraft as a reference in place of a pure INS. However, modifications to the transfer alignment algorithm may be required to cope with the intermittent nature of GPS signals in a military environment. A simulation study, using trials data from an aircraft INS/GPS, has been conducted to determine this. The performance of a conventional velocity-matching transfer alignment algorithm has been assessed using both the blended INS/GPS velocity and the corresponding pure inertial velocity as the reference. Where a GPS signal was continually available throughout the transfer alignment period, using the blended INS/GPS velocity as the reference resulted in a significantly more accurate alignment of the missile INS. Where the GPS signal is intermittent, the re-acquisition of GPS following an outage can cause a transient in the blended INS/GPS velocity. The simulations have demonstrated that these transients could seriously disrupt the transfer alignment process, resulting in significantly poorer alignment than that obtained using the pure inertial velocity as the reference. The disruption mechanism has been identified. It is thus concluded that, to obtain the accuracy benefits of using an integrated INS/GPS as the reference for transfer alignment without a loss of robustness, enhancements to the transfer alignment algorithm must be made.
Published in:	Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999) June 27 - 30, 1999 Royal Sonesta Hotel Cambridge, MA
Pages:	731 - 737
Cite this article:	Groves, Dr Paul D., "Transfer Alignment using an Integrated INS/GPS as the Reference," Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999), Cambridge, MA, June 1999, pp. 731-737.
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