SATELLITE SELECTION CRITERIA DURING ALTIMETER AIDING OF GPS

Barry A. Stein

Peer Reviewed

Abstract: The 21 satellite constellation envisaged for GPS yields occasional geometric configurations that result in poor navigation solutions. It therefore may be necessary to use altimeter aiding in these cases in order to improve the geometry. During altimeter aiding, only three of the visible satellites will be used in conjunction with the altimeter. It is of paramount importance to select the three satellites that will yield the best possible navigation solution when combined with the altimeter data. This paper presents a closed form algorithm for satellite selection. It differs from other satellite selection algorithms in that they use four visible satellites and do not consider the altimeter. Also, the usual problem of computationally inverting a 4 x 4 matrix is avoided. Computer simulations show that the algorithm avoids selecting any of the satellite configurations that would yield a poor navigation solution. A comparison has been made between using the true GDOP closed form solution and the maximum volume of a tetrahedron. The latter is shown to be an integral part of the former. Results indicate that it yields sufficiently accurate results under the assumed conditions.
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 32, Number 2
Pages: 149 - 157
Cite this article: Stein, Barry A., "SATELLITE SELECTION CRITERIA DURING ALTIMETER AIDING OF GPS", NAVIGATION, Journal of The Institute of Navigation, Vol. 32, No. 2, Summer 1985, pp. 149-157.
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