Freight train gauge-exceeding detection based on three-dimensional stereo vision measurement

We present a method for freight train gauge-exceeding detection based on three-dimensional (3D) stereo vision measurement. To reach high measurement accuracy under large-scale situation, the factors which influence the 3D measurement error are analyzed in detail. Algorithm to accurately extract the laser stripe feature projected by the measurement system is described. With the obtained stripe features, the 3D structure of the freight train can be reconstructed with nonlinear optimization procedure. Specially designed targets are used to identify the global coordinate system for gauge-exceeding detection. A prototype has been developed and the reliability and accuracy have been demonstrated by external field experiment.