A Near-Instantaneous Initialization Method for Attitude Determination

Patrick Y. C. Hwang

Abstract:	One characteristic that is desirable for any real-time attitude determination scheme using differential GPS carrier phase measurements is quick initialization to resolve carrier cycle ambiguities. Such a characteristic adds robustness to the scheme particularly when interruptions in signal tracking oc- cur by allowing for prompt resumption of operation when- ever the signal is reacquired. Most schemes available today attempt to resolve the initial integer (cycle) ambiguities by way of searching a limited domain of integer combinations. However, if the antenna separation stretches to the order of many wavelengths, this domain can become quite sizeable thereby requiring a longer span of observation data. On the other side of the coin, it is also important to maintain a wide separation of the antennas in order to obtain sufficiently good angular accuracies. A novel approach is proposed in this paper to resolve the initial integer ambiguities with a scheme drawn from a tech- nique that originated in kinematic surveying called the an- tenna exchange. Here, that technique is modified for situa- tions where a platform is never stationary but is continually in motion, an example of which may be a ship at sea, or a structure in space. The added dimension of motion necessi- tates the use of additional information to solve the problem. The integer ambiguities are resolved instantaneously upon completing the exchange procedure. The antenna separation can be as wide as the physical complexities of the antenna ex- change mechanism will allow. Simulation results verifying the operation of this scheme are presented together with is- sues of the antenna array design that will need to be consid- ered.
Published in:	Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990) September 19 - 21, 1990 The Broadmoor Hotel Colorado Spring, CO
Pages:	661 - 669
Cite this article:	Hwang, Patrick Y. C., "A Near-Instantaneous Initialization Method for Attitude Determination," Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990), Colorado Spring, CO, September 1990, pp. 661-669.
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