ANALYSIS AND CALIBRATION OF LORAN-C SIGNALS IN THE LOWER ST-LAWRENCE AREA USING GPS

Loran-C signals along and in the Lower St. Lawrence River, namely betw een Quebec City and the Gaspesia Peninsula on the south shore, between Quebec City and Havre-Saint-Pierre on the North Shore, and between Qu ebec City and Anticosti Island in the river, were analyzed using a mob ile Loran-C coverage validation and calibration system consisting of a nalog and digital Loran-C receivers, differential GPS and data logging systems. The road measurements were made successively during February -March and July-August 1991 to analyse seasonal effects. The signals r eceived from the East Coast Canada Chain (5930M, X, Y, Z) and the Nort heast U.S. Chain (9960M, W, X) are discussed herein. The Field Strengt h and Signal to Noise Ratio measurements are compared with predicted v alues using various models for conductivity and atmospheric noise. The Time Difference (TD) measurements are first compared between forward and reverse runs along the road profiles to ascertain the quality and reliability of the system utilized. The differences between Winter and Summer TD measurements are then analyzed. A relatively small but sign ificant seasonal effect is found. The GPS-derived TD distortions are c ompared with those derived using various models for the combined effec t of the primary, secondary and additional secondary phase lags. The d ifferences between measured and modeled distortions reaches several mu s. The effect of these differences on Loran-C positions is found to re ach several hundred metres in many cases. Conclusions related to the r esults presented herein are made, together with recommendations pertai ning to the use of these results and future investigations.