HARRISBURG, PA – The Pennsylvania Department of Transportation is in the middle of preparing specifications for using GPS technology that includes automated precision grading with bulldozers and motor graders, according to Constructioneer magazine. When this access road project is completed, it will link the airport to I-80, four miles to the south. I-80 is the main northern tier interstate highway running from New Jersey to California.

The technology being used is known as stakeless grading. This stakeless approach includes both rough grading and precision grading on all phases of road construction. The new GPS technology will help the grading operation hit a shorter completion date.

Mounted on the Caterpillar models D5N bulldozer and the 120H motor grader, and a John Deere model 770 motor grader, are Topcon 3D-GPS+ automated control systems. The D5N bulldozer also is used for rough grading, but its grading procedure is automatically controlled, and with the base station in place the grading tolerances are within 0.1 foot or less. Precise location points are achieved by triangulation. This system tracks all available satellite signals, thus assuring greater solution quality and integrity.

With dual-constellation tracking capabilities and the optional Co-op Tracking System integrated with the 3D-GPS+ Control System, satellite tracking integrity is maintained (locked) when the bulldozer or motor grader is grading near or under canopies such as trees. Added to the 3D-GPS+ Systems installed on the two motor graders is the optional Millimeter GPS System for an even more precise grading-control system. It enables the motor graders to automatically perform fine grading (measurable in millimeters) not readily reachable by using traditional staking or standard GPS methods.

Grading activities are verified by monitoring the grades at random points with Topcon Pocket-3D FC-100 field controllers running their Pocket 3D software in concert with PZS-1 mounted on the range poles.