A technology for sewer pipe inspection (part 1): Design, calibration, corrections and potential application of a laser profiler

In order to ensure and extend the serviceability of sewage infrastructure, sewer managers need more accurate data to estimate its actual state. For that purpose, various inspection techniques can be implemented. A first prototype of an unbiased laser profiler was developed to improve the accuracy of collected data (Clemens, Stanić, Van der Schoot, Langeveld, Lepot, 2015). However, a higher accuracy needs to be achieved. This article presents the results of an improved prototype that delivers an increase in the measuring accuracy of 5-10 times, which was achieved by using more accurate equipment (lasers and cameras) and by improvements in the methodologies applied (e.g. removing the last bias image distortion by camera calibration). The new design presented hereafter provides accurate measurements (σ < 2 mm) of cross section and accurate 3D image of a pipe. The potential applications of the improved laser profiling technique are comprehensive: e.g. deposit measurements, roughness measurements.