Demonstration of LiDAR on Accurate Surface Damage Measurement: A Case of Transportation Infrastructure

Accurate damage measurements of the transport infrastructure facilities during their maintenance/service life are characterized by their higher cost, safety hazards, historical data loss etc. Conventional techniques have limitations on their longevity and sustainability. To overcome this, many non-contact measurement technologies such as photogrammetric techniques, LiDAR etc., are demonstrated in various measurement-related applications. However, measurement accuracy in photogrammetric techniques is affected by many external factors, which discourage their wider usage as preferable measurement techniques. Many of these factors cannot be controlled by the surveyor/operator on the ground, but the scanner location, which plays a significant role on the accuracy of the collected point cloud data. Hence, there is a need for a guiding method to appropriately place the LiDAR towards achieving the targeted accuracy level. With this background, the study developed mathematical equations to understand the variation of point cloud density with respect to the location of LiDAR from the target surface. An interaction diagram is developed to accurately predict the effective scan area, with anticipated point cloud density/point spacing. A LiDAR-based measurement framework has been developed as part of this research. However, this paper only scope to elaborate on the evaluation of the developed framework's accuracy through a case study on an old bridge structure with surface damages. Upon post-processing the collected point cloud data, it is concluded that the proposed scan area planning framework using LiDAR can detect surface damages as little as 3mm on the highway bridge components accurately.