Simply attach a marker to a bridge and measure bridge deflection quickly, cost-effectively, and accurately using a standard digital camera. Rather than installing sensors, only a marker plate printed with a grid pattern needs to be mounted on the bridge. With conventional techniques, Moiré measurement is difficult when the area below the bridge is a river, railway, or road, as securing a camera position becomes problematic. The key advantage of the Moiré technology developed at AIST is that deflection measurement can be performed by shooting along the bridge axis regardless of conditions beneath the bridge — since the camera is positioned at the bridge abutment shooting along the bridge axis, conditions below the bridge are irrelevant. This technique is patented.

Leveraging this advantage, we have developed a new cloud-based continuous monitoring system that uses commercially available network cameras installed at bridge abutments to continuously monitor bridge pier displacement.

This was motivated by an increase in scour incidents — cases where the base of railway bridge piers is eroded and tilts during recent heavy rainfall disasters. The system offers superior cost performance compared to auto-tracking total stations, with the added benefit of being able to visually inspect site conditions via the camera feed when an anomaly occurs.

This continuous monitoring system can also be applied to railway track monitoring.

When pipes are installed directly below an operating railway track, or when construction work is carried out near an active line, it is essential to continuously monitor whether that work is causing track irregularity in the rail. Our system automates this measurement process and can send email alerts when an anomaly is detected. Experiments conducted in collaboration with Yahagi Construction Co., Ltd. have demonstrated that this rail displacement measurement achieves a sub-millimetre error compared to manual measurement at all times.