Bridge inspection
Bridge inspection with a 360° camera drone
Background
A large number of bridges are in use in Germany. These are an essential part of the road infrastructure and are considered a vulnerable element of the road network. Many bridges were built in the 1950s, 1960s and 1970s. As a result, many bridges are now between 40 to 60 years old and often suffer from corrosion and cracking. Defects in bridges can have serious consequences, ranging from traffic restrictions to bridge collapse. Maintenance of old bridges is complicated, expensive and time-consuming. Typically, bridges are manually inspected for damage in the field by having skilled workers walk onto the bridge and use scaffolding or aerial lifts to inspect the critical parts of a bridge that are not easily accessible. Therefore, visual pre-inspection of bridges using drones could reduce costs and increase the efficiency of the inspection process. Although the use of drones to inspect bridges is not new, standard high-resolution cameras have mostly been used under a drone for inspection. In contrast, this project uses a 360° camera on a drone to better inspect critical areas such as corners, arches, or the ceiling of the bridge.
Objectives
The objective of this research is to evaluate the use of a commercial drone with a top-mounted 360° camera for bridge inspections. To date, custom-built drones are often used for inspection. These can be very expensive and technically challenging. In order to keep the technical and financial effort as low as possible, commercially available products were deliberately used.
The first work objective is to review the literature on bridge inspections, visual crack detection techniques, and the use of drones for infrastructure assessment.
The second work objective is to use and test a commercially available drone equipped with a commercially available 360° camera to be used for bridge inspection. The 360° camera should be able to be attached using a simple and reversible method.
Further, to demonstrate that the drone can properly inspect a bridge for cracks and other defects using both the 360° camera and a standard camera on the underside.
Work objective four is to evaluate the results and compare the images from the standard HD camera with those from the 360° camera for crack detection.
Results
The bridge inspections we have conducted so far are limited to visual inspection with an HD camera under the drone and a 360° camera on the drone. In research, visual inspection with a drone is the most common application and we can confirm the successful use of this method from previous work by other researchers. However, the use of 360° cameras is very limited in the literature, and to our knowledge we are the first to use this technology for crack detection in bridges. A major disadvantage of using a camera above the drone is the reduced flight stability of the drone, which requires extreme caution when navigating.
Outlook
In bridge inspection, we have so far focused on visual inspection with digital images. Bridge inspection is a complex task and should rely on a variety of destructive and non-destructive techniques. It is therefore important that other techniques are used in combination with drones in the future. The current success rate of our crack detection algorithm is still relatively low and should be improved in the future. Another drawback is also that the thresholds for crack detection still need to be set manually. Future research should focus even more on automatic crack detection, e.g. using deep learning algorithms.
Project name
Bridge inspection with a 360° camera drone
Project leader
Prof. Dr. Andreas Humpe
Previous publications
Humpe, A. Bridge Inspection with an Off-the-Shelf 360° Camera Drone. Drones 2020, 4, 67. https://doi.org/10.3390/drones4040067
