Long Distance Video Camera Measurements of Structures

Tall buildings, long-span bridges, and other structures that have physical access issues can be difficult or costly to instrument to measure structural vibrations. Videos cameras offer a potential method for noncontact measurement of structures. Measurements have previously been made over long distances with targets placed on the structure of interest, however this addition removes much of the flexibility of using a camera in the first place. This paper will present a method for measuring displacements of structures from long range with a video camera in an uncontrolled and natural environment. The technique relies on optical flow processing of the video to determine the displacements of structures in the frame. A pilot study of a long range video camera measurement of a structure from a distance of over 500 feet will be shown as an example of the current possibilities of long range measurements. The issues of atmospheric turbulence and camera motion will be discussed and potential efforts in solving these issues will be described along with a discussion of camera requirements.