Parking lots always present a challenge to earthmoving contractors. Their irregular surfaces require extensive grade checking, and traditional rotating laser systems cannot be employed for machine control. Machine operators now skillfully grade these surfaces quickly and easily with the use of the Global Positioning System (GPS) for machine guidance, one of the most innovative areas of today’s construction industry.
At an Aurora, IL, shopping-center development, Trimble‘s SiteVision GPS Grade Control System guides a D8 dozer operator for jobs across the entire site: cutting roads; contouring parking lots, outlots, and pads; and digging and grading retention ponds. SiteVision is particularly useful when the dozer operator cuts slopes into the foundation for the parking lot.
According to Dave Kellogg of KR&G Excavating Partners LLC, “I felt that if SiteVision was accurate on vertical grade, it could do something that nothing else could do. Initially, I was concerned how GPS would handle elevation, but on a D8 it worked great. It’s easy to put the site to grade from high to low points using SiteVision. We also cut and shape the area faster. In the cut areas of parking lots we used it to our best advantage. That’s a job that laser guidance certainly can’t do,” since laser guidance is limited to making flat surfaces, and a parking lot requires the grading of a series of slightly concave bowls.
With SiteVision GPS, the operator views design plans, grades, and alignments on a screen that is easy to see in full daylight. While SiteVision displays machine position on a map, on-grade lightbars indicate how much to raise or lower the blade to cut/fill to match the design surface. With a single key press, the operator switches between a plan view and a cross-sectional view, showing the blade position relative to the design surface or alignment. With the site plan in the cab, bringing the site up to grade is faster and more predictable.
Before SiteVision GPS, grading a parking lot was very time-consuming and required many grade checks. It was the kind of job that needed personnel in front of the machine directing the operator how to cut. SiteVision changes the nature of the job completely. From inside the cab, the operator has all the necessary direction for precise grade control.
What is most dramatic is that, as the slope changes, the operator doesn’t have to wait for directions from a grade checker. As Kellogg affirms, “SiteVision made quite a savings because we didn’t need to check grade as we normally would. In fact, we didn’t need any checkers. A month of manpower was saved.” In-cab grade control allows operators to progress smoothly and efficiently without having to rely on external direction. Moving earth accurately with every pass also means less rework, faster job cycles, and reduced fuel and maintenance costs.
SiteVision GPS also eliminates the need for staking as the machine operator works to a design. Considering the job as a whole, Kellogg says, “The biggest benefit is being able to make cuts on areas where there are a lot of grade changes without even staking the area.” For example, the area to make retention ponds had to be heavily staked in the past because of their irregular shapes and different slopes. Generally these ponds gradually slope to a flat safety shelf, to protect anyone who might wade in and slip, before the bottom of the pond drops to a maximum of about 10 ft. SiteVision eliminates the need for staking and restaking as these ponds are cut.
“I really saw its benefit on machines that had to work an elevation, getting it closer to grade,” notes Kellogg. “It was very useful when we had to cut and shape to a 5- or 6-foot depth and even some areas that had an 8- or 10-foot fill. It’s great to see the cuts as they are being made. On a big site, it would be useful to have more than one SiteVision unit.”
The next use by KR&G for SiteVision GPS is on a 750 John Deere dozer at St. Charles, IL, a single family development, to perform cuts on roads, building pads, and rear yard swales. Whether it takes moving a hill in preparing a site or sculpting out a retention pond, SiteVision GPS is proving itself as a valuable tool that’s changing how dirt is moved.
