High-speed Laser Scanners for Railways and Roads

At INTERGEO 2010, the Freiburg based Fraunhofer Institute for Physical Measurement Techniques IPM had the latest developments in the field of fast distance measuring with laser scanners on show. Apart from their outstanding scientific expertise, the measurement technology specialists also presented their years of experience in building complete system solutions. In recent years Fraunhofer IPM has acquired numerous customers worldwide thanks to the institution’s tailor-made system solutions, particularly for railway-specific applications. Mobile mapping applications are growing in relevance in the road transport arena. This is where the fast, accurate, and eye-safe laser scanners from Fraunhofer IPM can prove their strengths as well.
New systems for railways

There are two different ways that laser scanners can contribute to smoothly flowing railway traffic:
For mobile applications, the scanner is mounted on the train and measures the desired position data of objects near the track while moving past them. For stationary applications, the laser scanner remains at a fixed position at a monitoring station next to the track and measures the geometries of passing trains.

•Contact wire position recording: Recording the position of the contact wire is a common application for use on inspection cars. Today, state-of-the-art complete systems from Fraunhofer IPM record 400 measurement profiles per second. In this way, at a speed of 100 km/h, the desired position data can be obtained for up to four contact wires simultaneously at intervals of 7 cm, along with online analyses.

•Detecting objects and structures near the rail track: Another mobile application serves to detect objects and structures near the rail track, such as platforms, tunnels, or bridges. The required position and safety clearance data are recorded with the help of a circular scanner mounted on the front of the inspection train. Fraunhofer IPM's basic scanner uses one laser beam and a scan frequency of 200 Hz, while the high-speed version has two laser beams and a scan frequency of more than 550 Hz.

•Train monitoring: Train monitoring performed directly in the course of normal railway operations can increase rail track safety significantly – particularly in sensitive track sections such as tunnels or bridges. To this end, monitoring stations are equipped with laser scanners from Fraunhofer IPM at suitable places alongside the track. Passing cars together with their freight can then be checked for geometric irregularities with 800 measurements per second. This means that at a speed of 100 km/h, the train's geometry is measured at intervals of around 3 cm.

Road data – a new application

Mobile mapping vehicles were also an important subject at INTERGEO 2010. These are measuring vehicles that record the road and its surroundings. Fraunhofer IPM has developed special high-resolution scanners for this application that scan the road surface. These so-called pavement scanners measure elements such as ruts, transverse grooves, or frost cracks with a view to obtaining data on pavement quality. Mounted on a vehicle at a height of around 3 m above road level, the laser scanner is easily capable of recording road surface widths of 4 m while delivering a resolution of less than 1 mm.