A high-speed laser-based profilometer has been designed and developed at the laboratory to measure surface profiles of roads and airfield runways. This report describes the theoretical and experimental studies carried out to identify and to evaluate the factors that influence the accuracy of measurement of the profilometer. Detailed comparisons between test profiles measured by survey techniques and by the profilometer are presented and discussed. The factors that are of most importance in determining the profilometer's accuracy of measurement are the imprecision in the determination of the non-colinearity of the laser transducers and in the transducers' calibration coefficients, together with the magnitude of the vertical temperature gradient across the profilometer beam and the effect of surface texture. Phase and amplitude comparisons show good agreement between profilometer and survey-measured profiles over the range of wavelengths that are of interest in studies of riding quality. In operation, the profilometer can measure road and runway profiles at speeds between 5 and 80 kilometres per hour but with an error that increases with speed. Facilities permit on-site analysis of the measured profiles and the measurement of surface texture if required. (Author/publisher)
Abstract