Including Deltarange Measurements in GPS-Aided Navigation Systems

Ralph E. Bach, Russell A.Paielli, B. David McNally and David N. Warner

Abstract:	The problem of integrating GPS with a conventional inertial navigation system (INS) is currently receiving much attention. The use of GPS code-tracking (pseudorange) measurements to aid the INS permits in- flight calibration and improves long-term position accuracy, even with interruptions in satellite visibility. The precise, independent measurements of GPS carrier phase, however, can be used to further improve the accuracy of GPS-aided navigation systems. This paper discusses and compares two methods for including the carrier-phase measurement known as deltarange with pseudorange for effective GPS aiding. The first method processes deltarange and pseudorange measurements separately in the navigation filter. The second method, based on carrier-smoothing, processes a “weighted sumn of pseudorange and deltarange measurements in the navigation filter. This method realizes the benefits of using deltarange with only half the measurement processing of the first method, and avoids the correlation introduced by carrier smoothing. Both methods require consideration of a “delayed-state” formulation, and a simplified algorithm for its implementation is presented. Evaluation of the methods is performed using data recorded during a flight test, flown in a terminal-area environment where differential GPS corrections were available, and where the aircraft could be laser-tracked to determine a “truth” trajectory.
Published in:	Proceedings of the 1993 National Technical Meeting of The Institute of Navigation January 20 - 22, 1993 Parc 55 Hotel San Francisco, CA
Pages:	131 - 142
Cite this article:	Bach, Ralph E., A.Paielli, Russell, McNally, B. David, Warner, David N., "Including Deltarange Measurements in GPS-Aided Navigation Systems," Proceedings of the 1993 National Technical Meeting of The Institute of Navigation, San Francisco, CA, January 1993, pp. 131-142.
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