A Method to Reduce Occlusion While Measuring Pavement Surface Profiles Using Triangulation Based Laser Scanners

Abstract

One of the considerations, in the characterization of pavement surface, includes an accurate measurement of the pavement surface profile. With the advent of modern technologies, automated methods (such as laser scanning) are being preferred over manual methods (such as the sand patch test). The laser scanning measurement method is based on the principle of active triangulation, where a camera (laser detector), a laser emitter, and the illuminated laser spot form a triangle. However, due to obstruction from other nearby parts of the profile, this triangulation may not get completed for certain points of the surface profile, leading to occlusion of some data-points. In such a situation, generally, as per the current practice for pavement surfaces, interpolation is used to estimate the height of the occluded data points. In this study, an approach is suggested where two laser emitters are used (rather than one) to reduce this occlusion. Thus, even if the camera cannot see a point illuminated by one laser emitter, it may be able to capture the same point when it is illuminated by the other laser emitter. This minimizes (in some cases, altogether eliminates) occlusion. Experimental results are presented to support this approach.