by Y. Chugui et al.
SPIE Newsroom, accessed 19 Jun 2007
One of many important railroad maintenance tasks is the inspection of the condition of the contact wire that supplies electricity to a train. Over long periods of operation the wire deteriorates, and these changes in its shape must be monitored. But measurement is tricky because the wire is always live, carrying up to several tens of kilovolts. A suitable system must permit evaluation of the height of the wire with a margin of error no greater than 0.2mm, and while the train is moving.