Measurement of Road Roughness by Low-cost Photogrammetric System

This paper discusses the continuation of the research work started in 2004. The previous results have been published both in ASPRS and ISPRS conferences. Now we intend to emphasize the latest developments and extended application areas of the system. Due to the increasing demand of the transportation authorities for rapid, accurate data acquisition about the road pavement, a mobile mapping system has been developed primarily for road surface detection. Our system involves a data archiving and system control unit (notebook), an imaging unit (two industrial cameras), a positioning unit (combined GPS/IMU system with built-in Kalman filtering), a marker unit (point-projection by laser diode array) and the mobile platform (pickup with special carrier frame and specified power supply). The first reported results were about creating the digital road surface model and detecting the cracks on the pavement. The system is now in test-phase at the road maintenance company of Budapest city (Municipal Public Service); during the practical tests several new demands have been raised. For the complex transportation management (scheduling road construction works, reconstruction etc.) the roads have to be classified into coarse categories. Therefore the resulted digital surface model has to be transformed into basic numeric form. Internationally, the so-called IRI (International Roughness Index) is used to represent the road condition. Besides the digital surface model of the road pavement, the INS measurements can be used without the images to derive data that indicate the pavement condition. Our experiments showed that vertical acceleration and the roll/pitch values are strongly correlated with the road roughness and waviness. Based on the single INS measurements, the roads can be classified into categories, our tests and initial results are also discussed in the paper.