Machine control and autonomous equipment is the use of GPS to guide a machine's blade or path to within a few centimetres, and, in some machines, to drive it with no driver. It is used on dozers, excavators and tractors.
The idea is simple. A GPS receiver on the machine gives its position. A computer holds a digital design, such as the exact level of a road. The computer compares the position of the blade with the design and moves the blade up or down by itself. The operator drives the machine, but the computer controls the depth. Because GPS can be accurate to a few centimetres, the machine can dig or level to the design without a person measuring each spot with stakes.
Ordinary GPS is accurate only to a few metres, which is not enough. For centimetre accuracy, a fixed base station at a known position on the site compares what the satellites tell it with where it really is. It sends the difference to the machine by radio or over the mobile network, and the machine corrects its own position. This method is called RTK (real-time kinematic) positioning.
For instance, a dozer operator at a highway site near Raipur is levelling the base of a road. The design says that the ground must be 30 centimetres below the old surface. The operator drives the dozer forward. The blade rises and falls by itself and stops at 30 centimetres, to within 2 or 3 centimetres. This saves money, because the machine does not dig too deep and then need extra material to fill the mistake. A tractor in a field works the same way, but the computer steers the wheels along a planned path instead of controlling the blade.
Some machines go further and work with no driver. Haul trucks in a mine and tractors in a field can follow a route alone. The stages from driver assistance to full self-driving are described in levels of autonomy.
Machine control acts on the machine, while a telematics device only reports on it. Machine control is used by construction equipment and by agricultural machinery. The machine's own GPS receiver gives its position as a latitude and a longitude, the same coordinates that digital maps and location data use. The machine's activity is also reported through a telematics device. Together, these belong to heavy equipment.