A New Algorithm for the Initial Alignment of Integrated INS/GPS Systems

Harry C. Strunz

Abstract:	We consider navigation systems consisting of a strapdown inertial sensor cluster, a single antenna GPS receiver, and associated electronics and software. In the absence of initial alignment information, such systems are required to determine their initial alignment to an Earth referenced coordinate frame, utilizing, for instance, conventional gyro compassing techniques. Typically, such systems will first utilize a “leveling” mode, followed by a “coarse align” mode. After the coarse alignment, the system may then enter the normal navigate mode. The “coarse align” mode is commonly mediated by a state augmented Kalman filter, which, together with the leveling mode, is often subject to operational and performance constraints. In this paper, we present an algorithm which performs the direct alignment solution of the integrated system, provided GPS only position and velocity data are available during the alignment process. A static (i.e., parked on the ground) or on-the-move (e.g., in-air) alignment is possible. This algorithm would execute during an initial alignment mode, which would replace the conventional leveling and coarse align modes. A Kalman filter is not used in this process, and the presented algorithm is believed to afford improved flexibility and performance for integrated navigation systems. The algorithm has been validated in a simulation environment.
Published in:	Proceedings of the 2000 National Technical Meeting of The Institute of Navigation January 26 - 28, 2000 Pacific Hotel Disneyland Anaheim, CA
Pages:	145 - 152
Cite this article:	Strunz, Harry C., "A New Algorithm for the Initial Alignment of Integrated INS/GPS Systems," Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2000, pp. 145-152.
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