Railway measurement techniques: Opportunities and challenges

Regular condition monitoring is an essential precondition for selectively planning maintenance operations, and eventually ensuring safe and reliable operation of railway lines. A running inspection train, or stationary check points equipped with different types of measurement systems for monitoring passing trains, is the most cost-effective way to do this. Such systems have to measure quickly and precisely under challenging conditions: they operate from moving platforms and have to cope with a high range of ambient temperature and light conditions, varying object reflectivity and harsh environmental conditions. Despite these adversities, railway operators demand precise measurement data, high data densities even at high travelling speeds and a user-friendly presentation of the measurement results. Laser scanning is the method of choice for fast and high precision measurement of track, overhead lines, clearance profile and rolling stock. Using laser scanners to monitor the infrastructure offers several advantages over conventional measurement systems. High point densities of up to some million points per second and accuracies of down to millimeters are possible. A considerable number of laserbased sensor systems for measuring railway infrastructure have been brought to market during the past years. The paper will give an overview about modern laser scanning methods, highlight assets and drawbacks, and describe selected railway measurement systems developed within the last years by the authors of this paper.