Scanning the roads most traveled
Germany’s network of highways and byways runs almost to the moon and back – at least in terms of distance covered – which can make keeping track of wear and tear a mighty task. But now a shoebox-sized laser device called the Pavement Profile Scanner (PPS) is helping to survey German roads at a brisk 100 km/h.
Developed at Fraunhofer Institute for Physical Measurement Techniques IPM in Freiburg, Germany, the scanner measures concrete and asphalt for condition and value. It measures the evenness of roads more rapidly, precisely and cost-effectively than other technologies and has shown success in railroad evaluation as well, according to the IPM team.
A single laser scanner attached to a vehicle measures the evenness of a road with a laser beam. Courtesy of Lehmann + Partner GmbH.
“One of the main factors is the quality of the surface, or, more precisely, its evenness,” said research leader Dr. Alexander Reiterer.
The high-resolution instrument measures road surfaces with a laser beam 4 m across at an acquisition angle of 70°; its vehicle mount holds it 3 m above the road. The device incorporates a rotating octagonal mirror, which steers the laser beam across the road perpendicular to the direction in which the vehicle is traveling.
The laser light is reflected from the asphalt back to the scanner, where it hits a detector chip. The distance between the scanner and the surface of the road can be determined by the amount of time it takes the laser light to travel back; measurements are accurate to between 0.15 and 0.3 mm, IPM reports.
The orientation and position of the measurement vehicle are acquired using the Global Navigation Satellite System and an inertial measurement system. Measurements are unaffected by external light conditions, Reiterer noted.
The scanner currently measures at a frequency of 1 MHz; the researchers want to increase this to 2 MHz, or 2 million measurements per second.
Road surveyors from Lehmann + Partner GmbH and IPM have used the eye-safe device to scan 15,000 km of Germany’s highways and roads. Next up: the runways at the airport in Hamburg.
“In the future, we want to go beyond surveying the evenness of a road and also detect tiny cracks in a targeted manner, which is a better way of preventing damage. Until now, this work has been carried out using cameras,” Reiterer said.
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