A GPS-Free Bridge Inspection Method Tailored to Bridge Terrain with High Positioning Stability

With the development of drone technology in recent years, many studies have discussed how to leverage drones equipped with sensors and cameras to conduct inspections under bridges. To address positioning challenges caused by the lack of GPS signals under the bridges, triangulation methods with on-site pre-installed Ultra-Wideband (UWB) sensors were used extensively to determine drone locations. However, the practical hurdles of deploying anchors under bridges are often overlooked, including variable terrain and potential electromagnetic interference from deploying a large number of UWB sensors. This study introduces a handover mechanism to address long-distance positioning challenges and an enhanced two-stage algorithm to enhance its suitability for bridge terrain with higher stability. By integrating these concepts, a practical bridge inspection system was devised, and realistic under-bridge experiments were conducted to validate the method’s efficacy in real-world settings.