The Global Positioning System (GPS) is a highly accurate satellite-based radio-navigation system providing three-dimensional positioning, velocity, and time information. GPS is an all-weather system that provides continuous worldwide coverage.
GPS receives signal from four or more satellites in view to calculate position, velocity, time, and other data as needed for precision construction applications. In construction, the position data is collected and used with site design files to provide cut/fill and horizontal positioning information to the operator.
GPS is a worldwide, 24-hours-a-day positioning system. GPS requires a clear view of the sky and works best in open areas. To initialize, an RTK GPS unit requires at least five satellites. After the initialization, an accurate position can be computed with a minimum of four satellites.
AccuGrade GPS is a family of products for machine grade control, designed specifically for earthmoving equipment in the construction industry. Trimble is the #1 GPS provider in the world. Caterpillar and Trimble setup a partnership to provide GPS solutions for contractors. After creating the partnership, they created the AccuGrade product line.
Trimble and AccuGrade are essentially the same products. AccuGrade machine control systems are built for ARO machines. ARO stands for AccuGrade ready option, meaning the machines are pre-wired from the factory ready to accept Laser & GPS equipment. Caterpillar is building their machines ARO ready right on the assembly line.
AccuGrade GPS is available for dozers, motorgraders, & excavators. Trimble systems are available on scrapers. It uses satellite positioning to provide blade guidance to the operator, or to automatically control the blade hydraulically.
For dozers and graders, AccuGrade GPS provides up/down and cross slope blade guidance as well as left/right direction to the operator using lightbars and an on-board color display. For scrapers, GPS provides up/down cutting-edge guidance with a single lightbar. The system includes a GPS receiver, a single GPS antenna and mast, and an on-board color display.
An optional automatic control kit provides direct input to the hydraulic valves to control the lift and cross slope of the dozer blade. The operator can drive anywhere on the job site and with the flick of a switch easily connect the machine’s hydraulic system to the GPS receiver and the design data to position the blade automatically.
By automating the final passes, operators can get complex jobs done faster than ever. Automating the blade control reduces site preparation time, minimizes operator fatigue and lowers operating costs, while giving you a consistently higher degree of accuracy.
To achieve stated specification for RTK GPS, it is necessary to use a Trimble RTK base station as part of the AccuGrade GPS setup.
AccuGrade GPS is compatible with any Trimble RTK base stations as long a suitable 900 mhz data radio is used. Site Vision Base Stations & SPS Site Positioning Base are compatible with AccuGrade GPS. In other words, if you have purchased a GPS Base Station newer than 2002, you won’t have a compatibility problem.
A single base station can support any number of machines within approximately 20 km (13 miles) of the work area. In order for this to happen, there must be uninterrupted radio communications between the base station and the machines. For best results, the base station is typically located on the construction site.
AccuGrade GPS configurations are currently available for dozers, motorgraders, excavators, and scrapers. Caterpillar & Trimble have thoroughly tested AccuGrade GPS operating on these types of machines. Other machine types will be supported in future releases.
AccuGrade GPS requires a digital site design (a digital terrain model or road design) in the on-board display. Using the GPS blade position and the blade cross slope, the ground elevation at the base of the blade is compared to the design elevation. The difference between the two elevations is the cut or the fill.
The lightbars provide 3D guidance to the operator. One of the lightbars is mounted horizontally in the center of the cab. Lights flash to indicate left or right, guiding the operator along a defined alignment. This alignment may be a road centerline, or edge of road, or any other line of interest.
The other two lightbars are mounted vertically and correspond to the right and left edges of the blade. Based on an input design file, cut or fill is computed for the base of the blade, and the lightbars direct the operator to raise or lower each side of the blade accordingly.
Several types of files are used by AccuGrade GPS: