The blade on an earthmoving machine is controlled by a semiautomatic method comprising a combination of a manual operational mode and an automatic operational mode. An operator first enters the manual operational mode and manually sets the height of the blade. The operator then enters the automatic mode and sets a reference pitch angle and an initial control point. The height of the blade is automatically controlled based on pitch angle measurements received from pitch angle sensors. Automatic control is effective over a particular range of soil conditions. When the automatic control range is exceeded, the operator manually shifts the control point, and automatic control resumes about the new control point. Blade slope is automatically controlled based on roll angle measurements received from roll angle sensors.