Megatexture measurement with a non-contact profilometer: accuracy of the method and parameters of influence
Megatexture corresponds to surface irregularities with wavelengths of a pavement profile lying between 50 mm and 500 mm and vertical amplitude ranging from 0,1 to 50 mm. Wavelengths of megatexture are the same order of size as tire/road interface. Megatexture is measured by a profilometer called RUGO (mlpc device) composed of a non-contact sensor, which measure the distance between its datum-line and the pavement surface examined. Then, the profile curve is analyzed by digital filtering technique in order to determine the magnitude of its spectral components at different wavelength. Thus, the texture spectrum of the profile is calculated with a texture level, given in dB, for each one-third-octave band and each path of measurement. This study investigates elements that may affect megatexture measurements like the type of captor, the speed or the operator. Experiments were realized in order to evaluate the reproducibility and the repeatability of the megatexture measurements following the international standard ISO 5725. In the first part, the device used and the information relative to the megatexture measurements and indicators are described. In the second part, the statistical analysis results are exposed and the value of repeatability r and reproducibility R are given for each one-third-octave band.