Story courtesy of Trimble

Novelist Alfred Doblin once remarked, "The world is made of sugar and dirt." For many dirt-moving contractors the sweet taste of success is being found with the help of automated grade control technologies that are providing precise, accurate results and a productivity-enhancing competitive edge. It is all about machine control.

Machine control runs the gamut from basic systems that rely on stringlines and lasers to highly precise 3-D GPS. Most of the systems currently in use were added to construction equipment as an after-market add-on, but now manufacturers are offering integrated systems at the time of manufacture.

There are three major categories of machine control systems available to the earthmoving contractor: laser-based display systems; laser-based grade control systems; and 3-D grade control systems.

Display Systems

Laser-based display systems are generally easy-to-use modular systems that are flexible and configurable to the machine and site needs. Used for machine guidance, these laser-based systems are found in a range of construction and earthmoving applications and machines including dozers, backhoes, scrapers, skid steers, and excavators.

The systems are elegantly simple to use and understand. Some contractors start out with a digital linear laser receiver that is mounted on the front of the machine atop a heavy-duty mast. Perched at a height above the operator's compartment, a number of the receivers provide 360-degree operation. The receiver is used as a stand-alone battery-powered display system for guidance. With the laser receiver, the operator has additional valuable information needed to perform grade work faster and more accurately.

Grade Control Systems

Laser-based grade control systems add proportional valve controls to the machine's hydraulics. Add a user interface and, voilá, the laser-based display system is upgraded to automatic.

When these changes are combined with an electric mast option, the laser receiver can be raised or lowered from within the operator's cab, saving the operator time and effort.

The signals from the laser receiver are used to control a proportional hydraulic valve for blade correction, allowing operators to grade faster and more accurately. This type of system is better suited to contractors involved in larger site preparation, such as residential and commercial site development.

Laser-based grade control systems have numerous benefits for the construction contractor including: reduced stakeout requirements, improved material yields and faster job cycles. The systems help contractors reduce costs, communication errors, reworks, and idle machine time.

3-D Grade Control Systems

Three-dimensional (3-D) grade control is a revolutionary change in earthmoving.

The 3-D system measures the X - Y and Z coordinates of the machine blade and compares that data to the preloaded digital terrain model. The design elevation and cross-slope for the current position are then calculated for the current position, and the system automatically moves the blade to the correct cut or fill position elevation and slope via the machine's hydraulics. Grade and slope information along with the blade's position is shown on the cab display.

GPS grade control systems can be precise to 30 millimeters and can enable operators to perform bulk earthmoving in a stake-less environment, using either automatic or manual blade control. When combined with an advanced tracking sensor, the grading accuracy can narrow to plus or minus 5 millimeters, which provides precise finished grade work.

Within 3-D grade control, there are two basic categories of systems: GPS grade control and Advanced Tracking Sensor (ATS) robotic total stations. Both 3-D systems provide the equipment operator with all the details of the automatic grade control system right at their fingertips. An on-board computer determines the exact position of each blade tip. It compares these positions to the design elevation and computes the cut or fill to grade. This information is displayed on the screen in plan view, cross-section view or text and on a lightbar display. The lightbar display, used for manual operation, guides the operator up/down for grade and right/left of a defined alignment. In automatic operation, the cut/fill data is used to drive the valves for automatic blade control.

Earthmoving is a requirement of practically every construction job. Advanced technology is taking design data from the office and putting it right into the machine cab, allowing operators to grade complex designs — such as vertical curves, transitions, super-elevated curves, and complex site designs — all without stakes, stringlines or paper layouts.

Because the data are there in the field, the site foreman or operator can quickly set the new grade or pad elevation right in the operator's compartment, without waiting for grade stakes to be set or repositioned. Additionally, the precision afforded by these technologies can provide material savings, better job estimates and reduced rework. It can also extend the work day into the night when necessary.

With the construction market becoming more demanding and competitive than ever before, contractors are increasingly turning to new technology for significant process and productivity advantages, reduced costs and greater efficiency. For earthmovers, that technology is machine control.