A process for determining the displacement of an entity equipped with a sensor for capturing a sequence of images, comprising a step for determining a motion vector associated with a current image as a function of at least one correlation calculation between a first block of pixels in the current image and a second block of pixels from which the vector points towards said first block of pixels, with said second block being in a previous image in the sequence of images, wherein the dimensions of the first block are determined as a function of at least a motion vector associated with a previous image in the image sequence.