J. Jarmulak, “B-scan Image clustering and Interpretation in Ultrasonic Rail-Inspection System”, in: ASCI’96 Proceedings of the second annual conference of the Advanced School for Computing and Imaging, Lommel, Belgium, June 5-7, 1996, Kerckhoffs, E.J.H., Sloot, P.M.A, Tonino, J.F.M, and Vossepoel, A.M. (eds.), ASCI, Delft, 1996, ISBN 90-803086-1-7, pp. 190-195. (pdf with high quality images , pdf with low quality images, copy text to clipboard works)
Dutch Railways use since 1976 an Ultrasonic Rail-Inspection System (URS) to inspect the railway tracks [Roos 90]. The inspection is done using a special coach. The coach has two assemblies of ultrasonic transducers (one per rail). In an assembly the transducers are placed at 0° and ± 70° angles (see Figure 1), providing information in 4 channels: 0° echo, loss of bottom echo, and ±70° echoes. The measurements are made every 2 mm along the rail.
Knowing the time elapsed from the send-pulse till the reception of an echo, the positions of the echoes are calculated [van’t Veen 95]. When indications coming from a section of the rail are put together, an image as in Figure 5a is obtained. Similar images are common in ultrasonic testing and are called B-scans, see for example [Hopgood et al. 93] where a method of interpreting ultrasonic images of welds is described.
2. Existing and new system
Once B-scan images of the rail are available, they have to be interpreted in order to detect any abnormalities which could point to possible defects (e.g. cracks). This task is at present largely done by a human operator. …