Abstract: Three-dimensional PIV of a free jet is given by means of the photogrammetryand image prcessing. In this paper,a new double-reflection method is being used to solve theproblems of synchronism and precision in the three-dimensional measuring of a high speedjet. The indices of refraction in water and air are considered,so the calculation of particle’s3-D position is correct. A succession of 3-D, global, instantaneous fields of particles andtheir velocity vectors have been reconstriicted by means of microcomput...