Dynamic Estimation of Rail and Highway Grade and Curvature

Dorota A. Brzezinska

Abstract:	The GPSVanTM is a mobile mapping and data collecting system developed at the Center for Mapping, The Ohio State University, that can map rail, highway, and transportation infrastructure while traveling at normal traffic speeds. The van technology combines a Global Positioning System (GPS) and a Dead-Reckoning System (DR) for the positioning of the vehicle, that is good up to 0.1 m when GPS data from at least four satellites are available at three-second intervals. An imagery module consists of a digital stereo camera system that records GPS time-tagged stereo images of the survey. Digital stereo pairs are processed to determine geodetic coordinates of the road features with a relative accuracy of 0.05 to 0.1 m within 10 to 40 m from the vehicle. The information collected by the GPSVanTM technology can be converted to formats required by Geographic Information Systems (GIS), and used by rail and transportation authorities to establish management priorities, and control safety features, such as speed limits, and location of the warning signs. The most important attributes needed to establish safety-control features are curvature and grade of the road. An eight-state Kalman filter, that completely describes the geometry and dynamics of the system, was developed for the purpose of instantaneous extraction of grade/curvature information from the positioning results. The major purpose of filtering is to provide internally consistent, instantaneous coordinates, azimuth, grade and curvature of the measured railroad. The total state vector consists of Cartesian X, Y, Z coordinates, azimuth, and curvature and its rate, together with slope (grade) and its rate. X, Y, Z coordinates, determined from the positioning module of the GPSVanTM software, constitute the observation part of the system. The variation in curvature is a consequence of the variability of the azimuth of the line. The curvature estimated here shows not only its value, i.e., inverse of the radius of curvature, but also the direction of the curve, i.e., decrease or increase of the azimuth, that corresponds to the opposite signs in curvature estimates. Grade is also estimated with the proper sign. This information is required by rail and highway databases. These databases are, for example, used by railroad traffic planners to generate optimum plans for operating trains, to slow, speed up, or reroute some trains, and to prevent train collisions. They are also extremely helpful for maintenance scheduling of track, signals, and telecommunication equipment of the railroad, and provide safety assurance for the repair crew [Sauer, 19951.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	1243 - 1251
Cite this article:	Brzezinska, Dorota A., "Dynamic Estimation of Rail and Highway Grade and Curvature," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 1243-1251.
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