How does 3D machine control work?

Many prospective 3D machine control system buyers quickly grasp the concept that a GPS/GNSS (Global Navigation Satellite System) antenna or LPS (Local Positioning System) prism mounted on the blade of a motor grader allows the position of the cutting edge of the blade to be known in real time. However, how the computer in the machine cab knows where grade is and how it gets that information deserves an explanation. What does a 3D machine control system do? A 3D machine control system essentially bypasses the traditional process of grade staking. Instead of giving site plans to the surveyor, who uses these plans to manually set the stakes and then having the machine operator visually read those stakes,