The general field of the invention is that of systems for detecting the posture of a mobile object. The systems according to the invention comprise a fixed electro-optical device comprising an emission source and a photosensitive sensor. The optical corner cube is arranged on the mobile object. The entry face of the corner cube has a predetermined geometry, the light coming from the source and reflected back by the corner cube forming a luminous contour on the matrix sensor. The fixed electro-optical device comprises an optical element with a known shape and location, which is placed in the vicinity of the said source and is arranged so as to form a dark zone in the central part of the luminous contour. The detection system comprises analysis means determining the position and the orientation of the mobile object from knowledge of the vanishing points of the luminous contour and the position and shape of the dark zone.