Bridges form an important part of the road systems. Monitoring them is essential for ensuring structural safety as overtime these bridges develop cracks, concrete spalling, and water leakage due to traffic loads, weather, and environmental exposure. Traditional visual inspections are often labor-intensive, costly and sometimes hazardous. Computer vision has made automated bridge inspections more practical. However, comparing damage captured months apart remains difficult because images are typically taken from different positions and viewing angles.
Now, researchers from Seoul National University of Science and Technology, South Korea, led by Assistant Professor Hyunjun Kim, developed an automated computer vision framework that tracks structural damage over time using drone images collected during routine bridge inspections. Their findings were made available online in Structural Health Monitoring on April 27, 2026.
This study enables long-term monitoring by combining artificial intelligence with three-dimensional (3D) bridge reconstruction. The 3D model of the bridge is built using images captured during the initial inspection. Images from subsequent inspections are then automatically aligned with this model using hierarchical localization and image clustering, allowing the same damage to be identified and compared over time even when photographs are taken from different camera angles or distances. Additionally, the framework uses Global Navigation Satellite System data to convert image measurements into real-world dimensions.
"Long-term structural monitoring requires more than simply detecting damage, it requires understanding how that damage evolves," says Dr. Kim. "Our framework allows engineers to visualize damage progression and measure its severity using images collected during routine inspections."
The system was validated over 120 days by monitoring an in-service prestressed concrete bridge using drone imagery. The framework succeeded in tracking the progression of cracks, spalling, and water leakage throughout the study period despite changes in camera viewpoint. It was able to measure the damaged areas with a maximum error of only 4.61% as compared to conventional manual measurements.
Unlike traditional inspection methods which could analyze damage only at a single point in time or which requires rebuilding 3D models for every inspection, this study suggests continuous monitoring of damage using a single reference model. This approach improves consistency while reducing the computational effort needed for long-term assessments. Although the current method is best suited for relatively flat structural components and its accuracy might differ on highly curved surfaces, it can report most bridge elements commonly encountered during routine inspections.
"We believe this framework can help engineers make more informed maintenance decisions and contribute to extending the service life of critical infrastructure." says Dr. Kim
As transportation agencies face aging infrastructure and increasing maintenance demands, researchers believe their study could support predictive maintenance strategies, improving public safety while reducing long-term inspection and repair costs. In future this technique could also be adapted to monitor other infrastructures such as tunnels, dams, and elevated rail systems.
