A displacement measurement methodology for deformation monitoring of long-span arch bridges during construction based on scalable multi-camera system

This study presents a scalable multi-camera system (S-MCS) for high-precision displacement measurement and deformation monitoring of long-span arch bridges during construction. Traditional methods such as robotic total stations (RTS) and single-camera systems face limitations in dynamic scalability, synchronous multi-point monitoring, and robustness against environmental disturbances. To address these challenges, the proposed S-MCS integrates dynamically expandable measuring cameras and dual correcting cameras to compensate for platform ego-motion. A self-calibration algorithm and spatiotemporal reference alignment framework are developed to ensure measurement consistency across evolving construction phases. The system was deployed on a 600-m-span arch bridge, achieving sub-millimeter accuracy (root mean square error ≤ 1.09 mm) validated against RTS data. Key innovations include real-time platform motion compensation, adaptive coverage expansion, and high-frequency sampling for capturing transient structural responses. Comparative analyses under construction loads, thermal variations, and extreme crosswinds demonstrated the system's superiority in tracking multi-point displacements, resolving dynamic behaviors and supporting safety assessments. The S-MCS provides a robust solution for automated, large-scale structural health monitoring, with potential applications in diverse infrastructure projects requiring adaptive, high-resolution deformation tracking.