Comparison of Alternate High Speed Rail GPS Locomotive Location Systems

K. Tysen Mueller and Richard Bortins

Abstract:	The US Federal Railway Administration is exploring technologies that will allow high speed trains to operate on the same tracks as freight and other rail traffic. The specific requirement is to automatically determine when a train has moved onto a siding to allow another train to pass with a confidence level of 0.99999. To achieve this confidence level requires that the locomotive location system have a lateral position accuracy of 0.41 m or a heading accuracy of 0.20 degrees for a high-speed (Type 20) switch. This study focused on the accuracy that can be achieved with locomotive location systems that use either a lateral position or a heading map matching algorithm. The lateral position accuracy was explored primarily with lab tests using data collected from a stationary GPS and DGPS antenna system. The heading accuracy was evaluated using data obtained from fixed antenna lab tests as well as dynamic field tests on a locomotive. The field tests involved a prototype GPS heading location system [1] that was mounted on a locomotive with data recorded for 3 days on several mainlines in the Pacific Northwest as well as in a rail yard. These measurements were post-processed to determine the raw and Kalmanfiltered GPS heading accuracy. A parallel track resolution (PTR) algorithm was also formulated to determine the probability that a train has entered the siding. This algorithm uses the estimated path distance traveled and a GPS rail map database to determine if the locomotive is passing over a switch. When the locomotive passes over a switch, the algorithm compares the rail database heading for entering the siding with the filtered estimate of the locomotive heading. Using the uncertainties in the path distance and the heading, the algorithm determines the probability that the train has entered the siding. This algorithm was evaluated for several mainline switches using the field test data and it was shown to achieve the required level of confidence for these switches. Results obtained with the GPS-heading based system established that the PTR requirements could be met based both on the lab and field tests. As expected, the GPS position-based system was not able to meet these requirements. The DGPS position-based system, however, was able to meet these PTR requirements if the position data is averaged over the period of one hour while a train is stationary.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	3095 - 3106
Cite this article:	Mueller, K. Tysen, Bortins, Richard, "Comparison of Alternate High Speed Rail GPS Locomotive Location Systems," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 3095-3106.
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