These systems allow the equipment operator to use GPS position data to make decisions based on actual grade and design features.
Some heavy equipment guidance systems can even operate the machine's implements automatically from a set design that was created for the particular jobsite.
GPS guidance systems can have tolerances as small as two to three centimeters making them extremely accurate compared to relying on the operator's skill level.
Since the machine's GPS system has the ability to know when it is off the design grade, this can reduce surveying and material costs required for a specific job.
[2] John Deere soon followed with their own version of ARO called "Integrated Grade Control" in 2006 on many Track-Type Tractors (TTT) and Motorgraders (MG).
Using two GPS receivers gives the guidance system two points of position allowing it to calculate what angle the machine is on relative to the site plan.
Machines that typically use indicate only consist of Soil Compactors (SC), Track-Type Tractors (TTT), and Motor Graders (MG).
Some projects such as clearing overburden at a mine site with a TTT, may not need two to three centimeter accuracy while as grading a road base with a MG does.
The advantages to this system is due to the accuracy that can be achieved with GPS and RTK, but requires an onsite base station.
The output from the GPS system is interpreted by the machine's electronic control module as a lever command given by the operator and moves the implements accordingly.
Track-Type Tractors TTT are an extremely popular machine platform for GPS guidance systems specifically in the smaller sized models that are used for fine grading.
Caterpillar Inc. and John Deere both offer fully automatic integrated GPS as an option from the factory on some of these models.
Motorgraders are another popular machine platform since they also perform fine grading activities that can benefit from the GPS accuracy.
Excavators use GPS technology in conjunction with angle sensors integrated in the machine's boom, stick, and bucket.
This allows the operator to see how deep they are digging by comparing the actual bucket location to the site design on the GPS display.
The GPS antenna is typically mounted on the bowl of the scraper and allows the operator to compare the depth of the cut versus the site plan.
As mentioned earlier, in order to increase the overall accuracy of GPS you have to purchase and use a base station, which adds additional cost.