Fast Non-contact Measurement and Alignment Method for Rail Profile Using a 3D Scanner

Miniprof is a rail profile measurement tool which can measure rail cross-sectional profile, and the measurement results can further be used for rail maintenance or other purposes. However, Miniprof only produces 2D contour at measured positions, and it requires high operational skills. This leads to difficulty for the operators to measure the rail profile at the same location correctly and often requires a long processing time for measurement. This paper introduces a method using a 3D scanner to accomplish fast non-contact 3-dimensional rail profile measurement from 3D mesh via raw point cloud data. The method utilizes the 3D meshes created from the standard 2D profile as the references, introducing an optimized Iterative Closest Point (ICP) algorithm to align 3D profile to the track reference coordinates. Experiments on a sample rail show that 3D profile can have less than 2 mm accuracy and 2D rail profile contour sectioned by 3D mesh has a similar level of accuracy (less than 1 mm) compared to the Miniprof measurements. Moreover, the analysis investigates the factors (such as the complexity of 3D reference models, the quality of scan models, and the initial alignments) that influence accuracy. This method can potentially increase work efficiency during the measurement of rail profile and can especially be useful for complicated rail profiled components such as switches and crossings.