Three-Dimensional Attitude Determination with the Ashtech 3DF 24-Channel GPS Measurement System

Kendall Ferguson, Joanna Kosmalska, Mark Kuhl, Jean-Marie Eichner, Kuba Kepski, and RezaAbtahi

Abstract:	A method for real-time, 3 dimensional attitude determination (heading, pitch, roll) has been developed using state-of-the-art GPS technology. This method is based on differential carrier phase measurements between four antennas which are connected to one 24-channel receiver. (The 24 channels are divided into four banks of six channels each.) Key advantages of this method over existing methods include the following: the initial phase ambiguity is determined with one epoch of data, the attitude is updated once per epoch, and cycle-slip detection and repair are achieved instantaneously. The differential phase measurements are processed using doublc- differecing techniques, which have already been proven successful in real-time kinematic applications. The attitude angles calculated can be as accurate as one milliradian (3.5 arc-minutes) for antenna spacings on the order of one meter. Since such accurate attitude measurements may be achieved in real time, numerous applications for the Ashtech Three-dimensional Direction Finding (3DF) system will arise. One obvious application is the integration of 3DF with an inertial measurement unit (IMU) for aircraft control and navigation. In this paper, we describe the basic system architecture of the 3DF system, the antenna conligurations, as well as accuracy of attitude as a function of geometry, baseline length, multipath, and number of satellites visible. Also shown are preliminary results from differential kinematic testing.
Published in:	Proceedings of the 1991 National Technical Meeting of The Institute of Navigation January 22 - 24, 1991 Sheraton San Marcos Hotel Phoenix, AZ
Pages:	35 - 41
Cite this article:	Ferguson, Kendall, Kosmalska, Joanna, Kuhl, Mark, Eichner, Jean-Marie, Kepski, Kuba, RezaAbtahi,, "Three-Dimensional Attitude Determination with the Ashtech 3DF 24-Channel GPS Measurement System," Proceedings of the 1991 National Technical Meeting of The Institute of Navigation, Phoenix, AZ, January 1991, pp. 35-41.
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