Abstract: The present invention relates to a control system. The control system controls the displacement of a working portion of an implement with respect to a reference position. The reference position can be the ground surface in the proximity of the working portion of the implement. A sensor is provided for determining the location of the ground surface to provide a reference signal. A signal generator is provided for producing a displacement signal which is representative of a preselected displacement. A comparator produces an error signal which is proportional to the sum of the reference signal and the displacement signal minus a null point signal. A servo mechanism is provided which is operable via the error signal to control the displacement of the working portion so as to substantially move the working portion the preselected displacement from the reference position thereby causing the error signal to be reduced to approximately the null point signal.