Abstract: The process performing a calculation of a motion vector field associated with an image, defining, for an image element with coordinates xi, yi, one or more motion vectors with components ui, vi, is characterized in that it also performs the following steps; modelling of the motion on the basis of a simplified parametric representation: ui=tx+k.xi vi=ty+k.yi with tx, ty components of a vector representing the translation component of the motion, k divergence factor characterizing the zoom component of the motion, robust linear regression in each of the two motion representation spaces defined by the planes and, x, y, u and v representing respectively the axes of the variables xi, yi, ui and vi, to give regression lines, calculation of the parameters tx, ty, and k on the basis of the slopes and ordinates at the origin of the regression lines. Applications relate to the selection of key images for video indexing or the generation of metadata.