A. Komjathy and R.B. Langley

Both at: Geodetic Research Laboratory, Department of Geodesy and Geomatics Engineering

University of New Brunswick, P.O. Box 4400, Fredericton, N.B. E3B 5A3 Canada

Phone: 1-506-453-4698, Fax: 1-506-453-4943, email: lang@unb.ca

Transport Canada Aviation, in conjunction with Cougar Helicopters Inc., initiated an in-service trial of helicopter precision approaches using local differential GPS (LDGPS). Cougar Helicopters, a Halifax-based commercial helicopter operator, equipped a Sikorsky S-76A helicopter with a Trimble TNL 3100 DZUS-mounted GPS/Loran-C avionics receiver. A high power TNL-2800G landing system base station at Halifax International Airport provided DGPS signals. Simultaneously, both at the base station and on board the helicopter, Ashtech LM-XII single frequency geodetic receivers collected data using the same antennas supplying the Trimble equipment. During the period of the 2nd of February 1994 to the 3rd of March 1994, ten different Cougar pilots flew a total of 65 approaches at the Halifax International Airport to test the performance of the system and collect data to analyze the accuracy of LDGPS guidance. It was necessary to carry out a detailed analysis of the Ashtech LM-XII ground truth system before using it as benchmark for evaluating the Trimble LDGPS. It is important to know how reliable the ground truth system is. We will describe the software used for processing the Ashtech LM-XII data, methods developed to evaluate the Ashtech solution, the results of the evaluation, and the conclusions about the reliability of the ground truth system. Once the data from the Ashtech ground truth system was processed and its solution and accuracy validated, we were able to use the C/A-code/carrier phase solution to compare with the Trimble local differential GPS (LDGPS) solutions. We will describe the software developed to perform the analysis of the comparisons. We will provide cross-track and vertical error assessment for a variety of approaches and develop statistics to quantify the agreement.


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This page was compiled by Attila Komjathy and last updated Wednesday, April 10, 1996. If you have any questions, comments please feel free to get in touch with me.

You can reach me at: komjathy@ocean.colorado.edu