Time-Based GPS Trajectory Guidance

Matt Jardin, Sundeep Bajikar and Jorge Heraud

Abstract:	Using the Global Positioning System (GPS) standard positioning service as a navigation sensor, a time-based trajectory guidance system i s developed. For demonstration purposes, a 2-dimensional (along-track and time) automobile guidance system is analyzed. Time-based trajectory guidance is achieved by using a GPS-driven real-time display to show the vehicle navigator the error between a baseline trajectory and the current vehicle position. The vehicle pilot is then directed to increase or decrease speed such that the baseline trajectory is followed precisely as a function of time. For the automobile guidance demonstration, a baseline trajectory was created by driving along a highway for about thirty minutes while making occasional speed changes and collecting raw GPS measurements. Simultaneously, GPS measurements were collected at a surveyed reference location so that carrier-aided differential GPS post-processing could be applied to the data to develop a very accurate baseline trajectory. The data runs then used carrier aided stand-alone GPS to create a display in the car to show the navigator the along-track position error between the baseline trajectory and the current trajectory in real-time. The driver was directed by the navigator to change speed as required to keep the position error as small as practical. The use of a velocity display was also investigated. Using these displays, the measured final time error at the end of the nominally thirty-minute baseline trajectory was less than the estimated 3 value of seven seconds in both real-time experimental runs. Some discussion is presented regarding the potential for applying time-based guidance to other vehicles, including general-aviation aircraft, trains, and ships.
Published in:	Proceedings of the 2000 National Technical Meeting of The Institute of Navigation January 26 - 28, 2000 Pacific Hotel Disneyland Anaheim, CA
Pages:	825 - 833
Cite this article:	Jardin, Matt, Bajikar, Sundeep, Heraud, Jorge, "Time-Based GPS Trajectory Guidance," Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2000, pp. 825-833.
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