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 retrore ective or painted targets on a wind-tunnel model. Custom software includes routines for image acquisition, target-tracking/identi cation, target centroid calculation, camera calibration, and deformation calculations. Applications of the VMD technique at ve large NASA wind tunnels are discussed.

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In image-based measurements, quantitative image data must be mapped to threedimensional object space. Analytical photogrammetric methods, which may be used to accomplish this task, are discussed from the viewpoint of experimental fluid dynamicists. The Direct Linear Transformation (DLT) for camera calibration, used in pressure sensitive paint, is summarized. An optimization method for camera calibration is developed that can be used to determine the camera calibration parameters, including those describing lens distortion, from a single image. Combined with the DLT method, this method allows a rapid and comprehensive in-situ camera calibration and therefore is particularly useful for quantitative flow visualization and other measurements such as model attitude and deformation in production wind tunnels. The paper also includes a brief description of typical photogrammetric applications to temperature-and pressure-sensitive paint measurements and model deformation measurements in wind tunnels.