A method and apparatus for using satellite positioning systems to more precisely locate the position of a portion of an attachment on an earthmoving machine is disclosed. More specifically, satellite positioning system antennas are mounted to an arm or other point relative to the arm of an illustrative excavator. A reference point relative to these antennas is used to determine the precise location of a portion of an attachment to the excavator, such as the prongs of a bucket. In one embodiment, an angle sensor or inclinometer is used to ascertain the position of the prongs when the bucket is scooped. In another embodiment, an angle sensor or inclinometer is used to measure the tilt of the body of the excavator, such as would occur when the excavator is resting on a sloped surface.