Videogrammetric model deformation measurement technique

The theory, methods, and applications of the videogrammetric model deformat ion (VMD) measurement technique used at NASA for wind-tunnel testing are pr esented. The VMD technique, based on nontopographic photogrammetry, can det ermine static and dynamic aeroelastic deformation and attitude of a wind-tu nnel model. Hardware of the system includes a video-rate charge-coupled dev ice camera, a computer with an image acquisition frame grabber board, illum ination lights, and retroreflective or painted targets on a wind-tunnel mod el. Custom software includes routines for image acquisition, target-trackin g/identification, target centroid calculation, camera calibration, and defo rmation calculations. Applications of the VMD technique at five large NASA wind tunnels are discussed.