Abstract: Disclosed is a method for the discriminating of obstacles by means of a radar, and its different applications to the measurement of a liquid in a tank or vessel, or again to the elimination of unwanted or parasitic echos coming notably from the ground, for radars mounted on vehicles or controlling vehicle traffic. To implement the method, the obstacle to be discriminated must have a substantially plane surface. The disclosed method then consists in successively transmitting substantially plane waves at slightly different angular frequencies .omega..sub.i, each wave being furthermore sent with two different polarizations p and p' chosen in such a way that these different coefficients of reflection on the obstacles according to the incidence of the waves give a criterion of discrimination. The processing at reception depends on the use (measurement of distance, elimination of parasitic echos etc.).