A method of analyzing return signals of successive range cells in a scene using constant false alarm rate adaptive control comprising, for each successive range cell in turn is disclosed mathematically. The return signal is processed mathematically and averaged over a predetermined number of cells near that cell. A first variable factor and the return signal for that cell, to derive a first result. The first variable is adapted depending upon that first result. A second variable factor is derived in accordance with a predetermined relationship between the first and second factors are mathematically processed. The second factor is mathematically processed. The second averaged return signal and the return signal for the cell, to derive a second result. The second result is used as an indication of the presence of an object of interest in the scene.