Real-time remote monitoring of dynamic displacements by computer vision

A system utilising computer vision has been developed to measure dynamic displacements in three dimensions in real time. It is particularly suited for situations where there is no local reference for the use of conventional displacement transducers, where a non-contact system is desirable, or for measurements at very low frequencies which may be below the range of other instruments. The system uses standard video equipment for its input and is therefore very flexible and relatively economical. Several targets may be tracked simultaneously using one or more cameras so many points may be monitored with minimal instrumentation. Tracking in 3D is possible by stereo viewing of a Target. This paper describes the operation of the system and presents some results from tests on a shaking table and on a cable-stayed bridge. A measurement accuracy of 0.5mm at a distance of over 200m has been achieved.