More Photogrammetry for Wind-Tunnel Testing

Abstract

964-971) has led to renewed interest in the use of photogrammetry for measuring the position, attitude, and deformation of a test article in a wind tunnel. The present research expands on this work with a more comprehensive mathematical model that can be used not only for determining the interior parameters of the cameras, but also the wind-off alignment of both the cameras and the test article relative to the wind tunnel. This calibration is achieved by combining data from multiple cameras and multiple model attitude settings in a single least-squares t, though (with eight cameras) as many as 94 t parameters can be involved. Similarly, data from multiple cameras are combined in a single sixparameter t to determine the position and attitude of the test article at wind-on conditions. Precision estimates of tted parameters are obtained through use of the covariance-matrix formalism and by bootstrapping. The model is demonstrated on data from two pressure-sensitive paint tests. An absolute accuracy of 0.01 deg for pitch measurements is demonstrated for this nonoptimized con guration. Suggestions for improvements are given for a dedicated optical model attitude measurement system.