Title: DIRECT-RANGING LORAN
Author(s): Leo Horowitz
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 17, Number 2
Pages: 200 - 204
Cite this article: Horowitz, Leo, "DIRECT-RANGING LORAN", NAVIGATION, Journal of The Institute of Navigation, Vol. 17, No. 2, Summer 1970, pp. 200-204.
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Abstract: This paper describes a straightforward software remechanization of conventional hyperbolic LORAN to provide totally passive, closed-loop, one-way direct range measurements to the individual LORAN transmitters instead of conventional "time differences" between LORAN transmitter pairs. No changes of any kind are required at LORAN transmitters to implement this technique; only essentially software modifications are required at the receivers. Preliminary analysis and simulation indicate that very substantial improvements in LORAN accuracy, coverage, and performance are gained by incorporation of this technique.' In addition, classic singularities on LORAN transmitter baseline extensions are removed, geometric dilution of precision (GDOP) characteristic of conventional hyperbolic LORAN is greatly reduced, and propagation anomalies contaminating LORAN appear to become measurable and removable. The redundant third range measurement provided by this technique suggests a straightforward 'Kalman Filtering implementation which provides optimum (i.e., minimum variance) real-time estimation and cross-calibration of LORAN errors. The author is indebted to Dr. Joseph L. Ryerson of USAF Headquarters for his original suggestion that geometric dilution of precision in conventional LORAN could be reduced if there were just some way of accurately measuring ranges directly instead of conventional LORAN time differences. This paper provides just such a way by taking advantage of additional information always available in conventional LORAN transmissions but previously discarded.