Abstract: A master slave steering system is provided for earth construction machinery having front and rear steerable wheels or tracks. A front steering sensor is connected to control the front wheel or track, and the rear wheel or track is controlled either from a rear steering sensor in an automatic mode or in response to the steering of the front wheel or track in a slave mode to insure that, in the automatic mode, the front and rear wheels or tracks are rotated independently as dictated by their respective sensors and, in the slave mode, the front and rear wheels or tracks are rotated in an opposite direction with respect to one another.

Abstract: In a slope control system for the working tool of a motor grader or other earth working machine, the slope sensor used for controlling the slope of the tool is mounted on a resolving platform below the front axle pivot of the machine to provide anticipation of the deviations of the machine from the gravity reference. The attitude of the slope sensor is corrected by a factor related to the angle of the tool with respect to the longitudinal axis of the machine.