Laser road surveyor is eyesafe, accurate to 0.3 mm

Freiburg, Germany--Alexander Reiterer and his team at the the Fraunhofer Institute for Physical Measurement Techniques IPM have developed the first laser scanner to be approved by the German Federal Highway Research Institute for measuring the evenness of roads. The technology, which has already proven its worth in railroad measurement applications, is fast, precise, and inexpensive: a single high-resolution laser scanner is all that is needed to scan and measure the road surface across a span of four meters with a laser beam.

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The scanner, which is the size of a shoebox, is fixed to the measurement vehicle at a height of 3 m. An octagonal rotating mirror in the device scans the laser beam across the road perpendicular to the direction of travel. An acquisition angle of 70° allows a scan of the entire width of any road up to 4 m wide from a standard vehicle. The distance between the scanner and the asphalt surface is determined from the time it takes the laser light to travel round-trip back to a photodetector; measurements are accurate to between 0.15 and 0.3 mm.

Unlike conventional measurement equipment, there is no need for broad attachments to be fitted to the vehicle. It must merely be ensured that the orientation and position of the measurement vehicle is known, which is done by using satellite reference systems like GPS (or the Russian equivalent, GLONASS) and an inertial measurement system. "Measurements are unaffected by external light conditions and can be executed at speeds of up to 100 km/h," says Reiterer.

The IPM’s pavement profile scanner has passed initial field tests. In cooperation with road surveyors from the firm Lehmann + Partner GmbH, the IPM has scanned 15,000 km of highway and other major roads across Germany since last summer. In spring, the measurement professionals will be measuring the runways at Hamburg Airport.