ABSTRACT
This paper describes a new laser-based system for non-contact measurement of the internal profiles of tunnels and other structures at speed. It has been developed for a railway application. Modern rail vehicles are larger than the Victorian vehicles for which Britain' s rail network was built; they operate much faster and the latest tilting vehicles lean into curves. Modern vehicles therefore pass much closer to the lineside structures . To run the trains safely at high speeds, it is necessary to have accurate up-to-date measurements of the space available. Most structures are stable but the track settles and is realigned, every 3 -6 months in some areas. Measurement of available clearance should ideally be performed at similar intervals .
