Roads are subject to severe strain in Finnish conditions. Especially in winter, their surface is damaged by large changes in temperatures, ground frost and mechanical wear caused by studded tyres. This causes deep ruts, potholes and cracks in road surfaces. Each year, some EUR 600 million are spent on fixing paved roads in Finland.
At present, there is no automatic method to identify paving damage and classify the condition of roads which makes analyses slow and expensive. A conventional analysis relies on a human’s ability to make observations and leaves room for interpretation.
The laser beam may offer a solution for the quick and reliable analysis of road conditions. A study in which mobile laser scanning is being developed to analyse the condition of roads has produced promising results.
FGI has studied how to analyse road conditions using a car-mounted laser scanner, which extensively scans the road and the driving environment, as well as another laser scanner mounted on an autonomous vehicle, which specifically scans the road surface. Laser beams are used to generate a dense point cloud dataset, based on which an accurate 3D model of the area is built.
‘Our goal is during the next three years to achieve a phase in which the method can be used in industrial sectors. In addition to analysing road conditions, the dataset has a huge potential in transport planning, noise modelling and identifying the location and condition of traffic signs, among other uses,’ says Professor Juha Hyyppä.
From rough estimation to precise measurement
Researchers have now reached a level of accuracy which corresponds to manually achieved results. Ruts have been measured repeatably, and the rut depth has been identified at the accuracy of a millimetre. Potholes, depressions and cracks have been detected in 75 to 80 per cent of all instances if their size was at least two centimetres. Conventional measurements only produce a rough estimation of road sections with surface damage.
Another significant difference compared with conventional methods is that measurements can be carried out in a moving vehicle, even at speeds of 80 km/h. The accuracy and speed of the measurements will be improved even further in the future, in addition to which the development of road damage over time can be investigated. The goal is to make mobile laser scanning a cost-effective option.
Research benefits not only road maintenance but also autonomous vehicles. Self-driving cars of the future require accurate and reliable real-time data on their surroundings and can use laser scanning to ensure safety when driving and to select the driving line while avoiding ruts. Furthermore, the laser scanning dataset serves to calculate high-definition maps used by autonomous vehicles with which they they can pinpoint themselves at the accuracy of roughly five centimetres without any satellite positioning signals.
In addition to paved roads, FGI has used similar methods to study the condition of forest vehicle trails and railway tracks. Research has been conducted in three projects funded by the Research Council of Finland.
Further information
Juha Hyyppä, Professor, Finnish Geospatial Research Institute of the National Land Survey of Finland, +35841 519 4451
Read more about the projects:
Read the article about railway measurement using mobile laser scanning.