An earthmoving system, includes in one embodiment a laser transmitter for transmitting a reference beam of laser light, and a laser receiver mounted on a mast on the bulldozer blade. The bulldozer has a frame and a cutting blade supported by a blade support extending from said frame. The blade support includes hydraulic cylinders for raising and lowering the blade in relation to said frame, and for tilting the blade along its length. The mast extends upward from, and is movable with, the blade. An inclinometer is mounted for movement with the blade to provide an indication of the inclination of the blade. A sensor detects turning of the bulldozer. A control is responsive to the laser receiver, to the inclinometer, and to the sensor, for controlling the operation of said cylinders and adjusting the position of said blade. When rapid turning of said bulldozer is detected the control operates to reduce the errors that would otherwise result from an erroneous inclinometer output.
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