Rho-Rho Loran-C for Offshore Surveys

• Published in: The Canadian Surveyor
• Main Authors: Eaton, R. M., Grant, S. T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1972
• Subjects: General Earth and Planetary Sciences; General Engineering; General Environmental Science; Lambda; Rho; Loran; Baffin; Newfoundland
• Online Access: http://dx.doi.org/10.1139/tcs-1972-0032; http://www.nrcresearchpress.com/doi/pdf/10.1139/tcs-1972-0032

Using atomic clocks, the United States Coast Guard has recently pioneered a precise distance measuring version of Loran-C, for positioning by two ranges when within about 1,700 km of the transmitters. In May 1971 the authors took advantage of the calibrated Decca Lambda survey chain, being used by the CSS Baffin on the Grand Banks of Newfoundland, to evaluate the accuracy and reliability of this ‘rho-rho’ Loran-C. This paper outlines briefly the principles of Loran-C and the associated problems of geodesy and radio wave propagation. The procedures for operating rho-rho Loran-C are described and the results of short term (hours) and long-term (weeks) accuracy tests are given. Rho-rho Loran-C is an ‘extrapolative’ navigation system that requires periodic checks at a reference point to adjust accumulated error. It was found that, by taking reasonable precautions, range measuring accuracy of about 200 meters can be maintained over five days or so.