A COMPARATIVE STUDY OF STRAPDOWN ALGORITHMS

C. R. Giardina, J. Heckathorn and D. Krasnjanski

Peer Reviewed

Abstract:	Four algorithms for computing the attitude matrix in a strapdown navigation system are described. The algorithms studied are Bortz g-direction cosine, Bortz-quaternion, Lie algebra and Cayley transform. Each algorithm has a fast cycle and a slow cycle. In the fast cycle short term attitude information is computed in a three parameter array. This information is then used to compute the attitude matrix in the slow cycle and the 3 parameter array is reinitialized at the start of the slow cycle. In the Bortz-quaternion and Lie algebra quaternion algorithms, the attitude information is resident in the quaternion and the attitude matrix then computed from the quaternion, whereas in the Bortz 9-direction and Cayley transform algorithms, the attitude matrix is directly updated. The attitude matrix computed from the Bortz 9-direction cosine algorithm is orthonormalized in a separate routine, whereas the Bortz quaternion and Lie algebra quaternion algorithms provide an orthogonal matrix which ia nor- malized by dividing by the length of the quaternion. The attitude matrix computed from the Cayley transform algorithm is inherently orthonormal. The overall computer efficiency is considered.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 28, Number 2
Pages:	101 - 106
Cite this article:	Giardina, C. R., Heckathorn, J., Krasnjanski, D., "A COMPARATIVE STUDY OF STRAPDOWN ALGORITHMS", NAVIGATION: Journal of The Institute of Navigation, Vol. 28, No. 2, Summer 1981, pp. 101-106.
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