Challenges in bridge inspection using small unmanned aerial systems: Results and lessons learned

Unmanned Aerial Systems (UAS) have gained considerable private and commercial interest for a variety of jobs and entertainment in the past 10 years. This paper presents the applications of UAS in transportation and structural engineering with emphasis on bridge inspection. A brief but thorough review of UAS applications for State Department of Transportation in the United States is provided. Potential advantages of UAS are acknowledged and the major challenges of using them for bridge inspections are determined. The feasibility of UAS in crack detection, real-time and post-processing, is studied through a case study in controlled conditions. In addition, fatigue crack detection in steel bridges is investigated using three platforms with different mounted cameras. The results of these case studies showed the possibility of using UAS for damage detection in concrete and steel bridges with comparable results with human inspections in real-time. At its best, current technology limits UAS use to an assistive tool for the inspector to perform a bridge inspection faster, cheaper, and without traffic closure. The major challenges for UAS are satisfying restrictive FAA regulations, control issues in a GPS denied environment, pilot expenses and availability, time and cost allocated to tuning, maintenance, post-processing time and acceptance of the collected data by bridge owners. Using UAS, with self-navigation abilities and improving image-processing algorithms to provide results near real-time could provide bridge inspectors with a useful tool to reduce costs and improve inspection quality.