Accuracy of a video odometry system for trains

Abstract

Reliable Data Systems is developing a video-based odometry system that enables trains to measure velocities and distances travelled without the need for trackside infrastructure. A camera is fixed in the cab, taking images of the track immediately ahead, at rates in the range 25–50 frames per second. The images in successive frames are ‘unwarped’ to provide a plan view of the track and then matched, to produce an ‘optical flow’ that measures the distance travelled.

The Study Group was asked to investigate ways of putting bounds on the accuracy of such a system, and to suggest any improvements that might be made.

The work performed in the week followed three strands:
(a) an understanding of how deviations from the camera’s calibrated position lead to errors in the train’s calculated position and velocity;
(b) development of models for the train suspension, designed to place bounds on these deviations;
and (c) the performance of the associated image processing algorithms.