1. An estimation method for estimating shifts of line images of an image, referred to as a “composite image”, made up of the juxtaposition of J line images, in which: the line images show portions of a scene on the surface (S) of a celestial body that are different and successively acquired by a row of sensitive cells of a sensor ( 10 ) on board a vehicle flying over said celestial body, each line image being composed of a plurality of pixels, and a line image L j , where 1≦j≦J, presents a lateral and/or longitudinal shift between the position that line image L j is destined to occupy in the composite image and the position it should occupy, because of a sighting error of the sensor ( 10 ) during the acquisition of line image L j , wherein the lateral and/or longitudinal shift of a line image L j relative to a line image L i , where j is different from i, is estimated according to a local model of lateral and/or longitudinal variation of the similarity between different line images, wherein the local model of lateral and/or longitudinal variation of the similarity between different line images is determined by calculating similarity values between different line images of the composite image, a step ( 20 ) of estimating the relative lateral shift δ j of line image L j relative to line image L i , during which the local model of lateral variation of the similarity between successive line images is determined by calculating similarity values of line image L j to line image L i for a plurality of lateral translation values of one line relative to the other, the relative lateral shift δ j is estimated as the lateral translation for which the value of the model of lateral variation of the similarity is maximum, and a step ( 21 ) of integrating relative lateral shifts δ j in successive line images, for determining cumulative lateral shifts δ′ j with respect to a reference line image of the composite image.