The application of Doppler based, LIght Detection And Ranging (LIDAR or lidar) technology for measuring true ground speed in a non-contacting manner is investigated, as a replacement to wheel tachometers that are commonly used for such measurements. Measuring track speed and distance traveled is an essential part of rail geometry measurement systems. Wheel tachometer measurement accuracy can often be adversely affected by wheel vibrations, change in wheel diameter, and wheel slip in high traction conditions. LIDAR is a non-contact measurement device that uses the Doppler technology to accurately determine speed. Two LIDAR sensors are attached to the underside of a track geometry car with the sensors’ Class I laser beams facing the gauge corner of each rail. The LIDAR sensors measure the absolute ground speed for each rail, allowing for the determination of forward speed and track curvature. The results of the tests show high accuracy in LIDAR speed, distance, and track curvature measurements when compared with other conventional means that are used in the railroad industry and ground truth measurements. With further development, LIDAR sensors can replace wheel tachometers that are commonly used for speed and distance measurement, therefore eliminating the problems with mechanical reliability and the need for periodic calibration of wheel tachometers.

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