Loran-C Calibration Using Navstar Differential Navigation Offshore Canada's East Coast

J. Hagglund, G. Lachapelle, H. Eaton

Abstract:	The NAVSTAR Marine Differential Navigation technique was used by Nortech Surveys during the summer of 1984 toprovide the positional information required by the Canadian Hydrographic Service during their calibration of Loran-e chains along parts of Canada's East coast. The minimum acceptable fixing time for an economically feasible project was three and a half (3.5) hours per day with a maximum allowable position error of twenty five (25) metres over distances of up to eight hundred fifty (850) kilometres. This criterion was shown to be achievable by two days observation between known stations in Dartmouth and St. John's, Newfoundland which are nine hundred (900) kilometres apart. Differential positioning using a range correction method showed positional accuracies of about five (5) metres (one sigma) with baseline distances of three hundred ten (310) and six hundred thirty five (635) kilometres. The project was carried out under contract for the Canadian Hydrographic Service. The GPS equipment utilized consisted of two Nortech TI 4100 receivers. The methodology used is described together with results in terms of accuracy, type of differential corrections used, number of usable hours per day and general performance of the GPS Satellites and receivers used. The accuracy in terms of the length of the baseline used for differential navigation is analysed. The actual calibration of loran-e from these positions was done by an inverse solution between the differentially derived GPS fix positions and the known loran-e transmitter positions. The distances were then compared against the loran-e measured ranges which had been corrected for phase lag as if the entire distance were over water. The difference was used by the Bedford Institute of Oceanography to modify the Loran-e lattices plotted on new charts to reflect additional secondary phase lag (ASPl) due to overland path. The main emphasis of this paper is on the accuracy of the GPS differer:tial fixes used for this calibration and the results of the additional secondary phase lags derived will be covered in another paper.
Published in:	Proceedings of the 1985 National Technical Meeting of The Institute of Navigation January 15 - 17, 1985 San Diego, CA
Pages:	18 - 24
Cite this article:	Hagglund, J., Lachapelle, G., Eaton, H., "Loran-C Calibration Using Navstar Differential Navigation Offshore Canada's East Coast," Proceedings of the 1985 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1985, pp. 18-24.
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