Advanced Imaging


Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Imaging Solutions of the Year: Monitoring Channel Tunnel Infrastructure without Obstructing Rail Traffic

Category: Commercial Applications
Close-up of the system conveyor in place in one of the tubes.
The 'workzone' inside one of the tubes.
Composite images of Channel Tunnel exit + cable close-up + cable in-situ.

By Advanced Imaging Editorial Staff

New Vision Technologies (Champs-sur-Marne, France)
(Nominated by Amanda DiBenedetto, National Instruments Corporation, Austin, TX)

The Challenge:

The Channel Tunnel is a set of three tubes, 50 kilometers (31 miles) long, which lie beneath the English Channel at the Straits of Dover, connecting Folkestone (Kent, UK) with Coquelles (near Calais, France). It is the second-longest rail tunnel complex in the World, surpassed only by the Seikan Tunnel at the Tsugaru Straits in Japan. Operated and maintained jointly by Eurotunnel plc (UK) and Eurotunnel SA (France), in 2004 the Channel Tunnel transported 1.3 million trucks, 2.1 million cars and 63,500 motor coaches, nearly 7.3 million Eurostar passengers and 1.9 million tonnes (~2.1 tons) of freight.

With so much rail traffic, Eurotunnel engineers need to measure wear and tear along the entire length of electrical contact cabling inside the Channel Tunnel and do so without disrupting traffic. Furthermore, the exact position and dimensions of any deterioration have to be documented.

The Solution:

The contact cable is lighted by a halogen metal iodide illuminator. Wear areas appear shiny against a dark background. Images are acquired by a monochrome, CMOS area-scan camera at up to 500 frames per second. Each wear area’s perimeter (640×100 pixels) is obtained by thresholding the image.

The field-of-view’s width covers the maximum cable offset while its height is sufficient to gauge the overall cable wear. Measurements are made 100 times per second and wear area parameters are updated at 50-millimeter (~2-inch) intervals. In order to avoid light-level variation, the threshold is re-adjusted as a function of the cable’s position in the image.

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