An apparatus (10) and method for determining the position of a work implement (12) movably connected to a machine (16) utilizes first and second electromagnetic radiation receiving devices (18, 20) connected to the work implement (12) at predetermined spaced locations. A processor (24) determines the first and second current coordinate positions of the first and second receiving devices (18, 20) in a site coordinate system based on position signals from the first and second receiving devices (18, 20). The processor transforms the first and second receiving points (R, L) from a local coordinate system related to the machine (16) to the site coordinate system using a plane (98) passing through the first and second current coordinate positions and a mid-point (C) located along a substantially straight line (99) passing between first and second previously defined coordinate positions of the first and second receiving devices (18, 20). The processor (51) corrects the position of the first and second receiving points (R, L) in the site coordinate system based on sensed changes in the pitch of the implement (12).