Videogrammetric model deformation measurement technique

The theory, methods, and applications of the videogrammetric model deformation (VMD) measurement technique used at NASA for wind-tunnel testing are presented. The VMD technique, based on nontopographic photogrammetry, can determine static and dynamic aeroelastic deformation and attitude of a wind-tunnel model. Hardware of the system includes a video-rate charge-coupled device camera, a computer with an image acquisition frame grabber board, illumination lights, and retroreflective or painted targets on a wind-tunnel model. Custom software includes routines for image acquisition, target-tracking/identification, target centroid calculation, camera calibration, and deformation calculations. Applications of the VMD technique at five large NASA wind tunnels are discussed.