Researchers have unveiled a real-time structural monitoring system that uses Global Navigation Satellite System (GNSS) technology to track both displacement and orientation in long-span bridges. This integrated approach marks a significant improvement over traditional systems that focus solely on movement and miss subtle rotational changes indicative of early structural stress.
The new met by Riko Seibo
Tokyo, Japan (SPX) Jul 30, 2025
Researchers have unveiled a real-time structural monitoring system that uses Global Navigation Satellite System (GNSS) technology to track both displacement and orientation in long-span bridges. This integrated approach marks a significant improvement over traditional systems that focus solely on movement and miss subtle rotational changes indicative of early structural stress.
The new method, called Integrated Displacement and Attitude Determination (IDAD), employs multiple GNSS antennas strategically placed along a bridge to monitor pitch and heading in tandem with positional shifts. Developed by a Southeast University-led team and tested on the Forth Road Bridge in Scotland, the system demonstrated sub-centimeter accuracy in displacement (0.004-0.006 m horizontally, 0.008-0.010 m vertically) and micro-degree precision in attitude (pitch 0.0013, heading 0.0004) across baselines up to 2 km.
At the core of the IDAD framework lies the Unscented Kalman Filter (UKF), which fuses the displacement and attitude data streams in real time while resolving GNSS signal ambiguities. The method allows engineers to observe bridge reactions to wind, thermal changes, and other environmental forces with unprecedented clarity. Field tests during winter storms highlighted the system's sensitivity, revealing small heading and pitch shifts that signal stress before visible damage appears.
"By integrating displacement and attitude into one estimation framework, we're capturing a dimension of structural behavior that has been largely overlooked," says Professor Xiaolin Meng, senior author of the study. "This level of insight allows us to better understand how bridges breathe and bend - vital knowledge for proactive maintenance and public safety."
Beyond bridges, the technology holds promise for other infrastructure such as high-rise buildings, offshore rigs, and dams - any setting where micro-movements can precede failure. Its reliance solely on GNSS, without inertial sensors, simplifies implementation and reduces cost. The research also opens the door to combining GNSS with inertial measurement units (IMUs) in future high-frequency monitoring systems capable of operating in complex environments.
As global infrastructure continues to age, the ability to detect and interpret structural changes in real time could transform how we manage public safety and resilience.
Research Report:GNSS integrated displacement and attitude determination for structural health monitoring of long-span bridges
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