Mono and stereoscopic image analysis for detecting the transverse profile of worn-out rails

Over its useful life a railway superstructure is subject to manifold mechanical and environmental stresses which gradually lead to its deterioration and consequent damage to comfort and speed safety. For several years the use of high-efficiency laser techniques has become consolidated and implemented in diagnostic trains (e.g. the train Archimede) which allow to detect the track geometric parameters and its state of wear with very high precision. The purpose of this paper is to suggest a new procedure for reconstructing the transverse profile of rails in operation by means of image-processing technique. This methodological approach, which will be detailed in the following paragraphs, is based on the “information” contained in high-resolution photographic images of tracks and on specific algorithms which allow to obtain the exact geometric profile of the rails and therefore to measure the state of the rail-head extrados wear. The analyses and the results, obtained from laboratory researches, concern rail cross sections taken from railway lines under upgrading by means of mono- and stereoscopic methods which, thanks to their characteristics, are appropriate to be employed in laboratory applications (mono techniques) or in high-efficiency surveys in situ through equipment directly installed on diagnostic trains, together with methods traditionally used.