Multi-Antenna GPS Reception with Vehicle Flexure

In Soo Ahn and Jim Sennott

Abstract:	To maintain signal continuity and vehicle attitude in critical real-time systems, multi-antenna diversity reception aboard the vehicle is essential. Important applications are: a) shiprelative DGPS reference, b) space structure attitude determination and relative positioning, and c) earth moving equipment guidance and control. For antenna diversity reception processing, including integrity monitoring, navigation-frame antenna offsets substantially more accurate than currentepoch double-difference solution values are needed. Driving uncertainties are body flexure drifts and inertial measurement biases and drifts. As vehicle antenna-antenna baselines increase, it becomes necessary to explicitly incorporate flexures in the system model. In this paper we address the reception problem in the presence of vehicle flexure, for multi-antenna multi-inertial sensor networks. Carrier phase observables are available at each antenna location, as are delta-theta and delta-velocity observations from each of the IMU sensor sites. Each IMU sensor is modeled with a standard 15-state model, which includes gyro and accelerometer biases and noise processes. IMU and antenna body frame location offsets are approximated with displacement and velocity drift processes, in three axes. The paper establishes the filter structure and related covariance formulation, including detailed development of system error state dynamics, linearized coupling of nominal dynamics into the system state transition matrix, and coupling of error states into the observables. The examples discussed are limited to single and dual IMU systems. With the covariance formulation in place, the paper then explores system performance. The performance metric is relative antenna positioning error in the navigation frame, normalized by single-epoch positioning uncertainty. Performance is explored as function of single and dual IMU setup, IMU quality, antenna spacing, and flexure process spatial and temporal correlation parameters.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	1948 - 1955
Cite this article:	Ahn, In Soo, Sennott, Jim, "Multi-Antenna GPS Reception with Vehicle Flexure," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 1948-1955.
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