This paper presents the PIV evaluation method used by IMAG for the PIV challenge 2001. This method is derived from an Optical Flow (OF) computation method based on Dynamic Programming called "Orthogonal Dynamic Programming" (ODP). It has already been presented in the general context of optical flow computation and in the context of Particle Image Velocimetry. In this paper, we try to present the core of the method in a more formal and more rigorous manner. Section 2 reformulates the PIV/OF problem as the search for a vector field minimizing the motion compensated image sequence time disparity. Section 3 explains the core of the ODP method based on elastic strip matching embedded in a multi-resolution iterative process.