UAV Photogrammetry for Monitoring the Cold Asphalt Patching Pothole Repairs

Cold mix patching materials (CMPMs) have become increasingly popular solutions for the emergency asphalt repairs of small- to medium-sized potholes in severe winter conditions or where short reopening times are required. Their performances need to be carefully monitored in the early post-application phases, when these materials have a high potential to face several distresses. The research aimed to identify a set of methods for the rapid and cost-effective acquisition of asphalt pavement surface geometric data to analyze the effectiveness of a given CMPM, with particular attention to procedures that minimize interference with the normal traffic flow or limit the lanes closure whilst ensuring the safety of operators and pedestrians. A road trial section in a sub-urban industrial zone, where ideal potholes were cut and filled with different types of CMPMs, was set up for this purpose. A low-cost unmanned aerial vehicle (UAV), was used for the experiments, repeating the drone survey in four successive epochs (up to 30 days). The captured images were post-processed with a photogrammetric software and the co-registered point clouds at the different epochs were compared to highlight the early patches performances and deteriorations. This ready-to-use methodology, tailored on the urban scale, made it possible to identify over time the occurrence of raveling on the patch area and to monitor the trend of patch surface depressions, extracting desired transverse and longitudinal profiles.