ELEMENT ASSEM. 9H9998 - Caterpillar

Illustration 1 g01117754
Process map of required items to get a functional AccuGrade® System on site.If the design does not change, the AccuGrade System does not need any other inputs. If changes do occur to the design, the site manager and operator can respond quickly once the updated design is provided, without waiting for surveyors and stakes. The AccuGrade System is also easily expanded onto other machines. Since the base station can support any number of machines, adding GPS grade control to other machines is simply a matter of installation.
Illustration 2 g01218400
Block diagram of the AccuGrade SystemThe Global Positioning System (GPS)
GPS is a system of satellites that orbit the earth twice a day at very high altitudes. The radius of the orbit is approximately 26600 km (16528 miles). GPS was set up by the government of the United States. GPS provides precise timing and positioning anywhere on earth, 24 hours per day with no charge to users.The GPS Receiver computes a position that is based on radio signals that are received from several different satellites. The satellites have highly reliable clocks, so the timing of these satellite signals is known very accurately. The GPS Receiver calculates the relative distance to each of the satellites. This calculation is based on the travel time of the signal and the speed of light (speed of the signal). The receiver then uses these distances in order to calculate the receiver's location on earth.As a broadcast only radio system, GPS supports an unlimited number of users. The broadcast frequencies penetrate clouds, rain, and snow. GPS can also accurately guide operations in fog or dust as well as at night. There are different levels of precision and accuracy available from GPS. These levels depend on the GPS Receivers and the methods that you use.The four basic levels of position accuracy (1 sigma) that are available in real time from GPS are as follows:
Autonomous, 10 m (30 ft) to 15 m (50 ft)
DGPS, 0.3 m (1.0 ft) to 1.0 m (3.0 ft)
RTK (Float), 0.2 m (0.7 ft) to 1.0 m (3.0 ft)
RTK (Fixed), .02 m (.07 ft) to .03 m (.10 ft)Illustration 3 shows the accuracy levels of the GPS.
Illustration 3 g01015622
Accuracy Levels Of The GPS (1) "Autonomous" (2) "DGPS" (3) "RTK Fixed" (4) "RTK Float"The method that is used for machine grade control in construction is the same as that used by surveyors for stakeout in construction. The method is called "Real-Time Kinematic" (RTK), GPS. This method provides RTK Fixed (centimeter level) solution.In order to produce RTK positions two GPS Receivers are required. One receiver is known as the GPS Base Station and is fixed in one place. The other GPS Receiver is known as the rover. This receiver can be stationary or mobile. The AccuGrade System utilizes two GPS Receivers on the machine (rover).The base station communicates to the rovers through a wireless data link using a data radio. Illustration 4 shows this setup.
Illustration 4 g01121908
GPS and the AccuGrade System (1) GPS satellites (2) GPS Base Station and