Machine control: Getting good grades is faster and easier
February 1, 2013 by David Godkin
Forty-five years ago it was my first job; a skinny 17-year-old kid working on a 50-km stretch of dirt, soon to be Highway 103 East from Hubbards to Halifax. A simple job, too: Place a small stone on a stake at the side of the alignment to indicate a fill, a small stone and a leaf to indicate a cut. All day I’m doing that, with the foreman periodically measuring the cross slope of each graded section with a crown board, slashing an “X” in the dirt where a deeper cut was required or an “O” for more fill. Then we’d start all over again, cutting and filling until the dirt surface was as finished as we and the grader operator could make it.
Prehistoric by today’s standards? You bet. In fact, these days grade checkers, surveyors and equipment operators are finding their jobs a whole lot easier not because of what’s there in the dirt at their feet but more than 20,000 km overhead: 24 satellites, each positioned so that no fewer than four transmit signals at any given moment to help us triangulate the length, width and elevation of our positions on the ground. This simple principle has been revolutionizing the way many contractors build roads and highways since the late 1990s. Others are less convinced—in part because of acknowledged costs, but also because of misunderstanding about what GPS can and cannot do.
More than a game of inches
All projects begin with a job plan, of course, but increasingly contractors are relying on 3D digital job plans loaded into a machine’s GPS control box and remotely connected to a nearby base station where satellite signals are closely calibrated to indicate the position of the machine on the ground and the grading tolerances it must work to. Instead of relying on stakes positioned every 25, 50 or 100 feet, 3D machine control “checks grade everywhere at every position and every location along the job site. So you’re not only accurate at every grade stake but every inch between all those grade stakes, too,” says Chris Mazur, North American product marketing manager for Leica’s machine control division.
Working in tandem with the machine’s hydraulics and the angle sensors mounted on the bucket or blade, GPS increases productivity and accuracy, and reduces the number of passes the machine has to make to come to grade.
“If I can get the grade in three passes instead of six or seven I’m going to burn a lot less fuel and save money, and I’m going to put a lot less wear and tear on my machines,” says Topcon Positioning System’s product manager Tony Vanneman.
It also means less wear and tear on machine operators, and a significant reduction in the amount of engineering and staking required on job sites. “You still have benchmarks on any project, but you can literally get by with 90 per cent reduction in staking because now all that information is in the operators machine or in the field controller of the grade setter.”
Trimble Navigation’s sales engineering manager Lamar Hester says GPS also helps dozer and grader operators work faster, particularly when blue topping. “They can run at a constant speed, not having to slow down, cutting it to fine grade…so they do pick up their speed when they’re operating with machine control.”
Every bit as important as the hardware, software development gauges and improves work flow from the standpoint of those
administering the job back at the office. Trimble’s “connected site strategy” streamlines work flows by connecting the machine in the field via the internet to the office where staff track the progress of the job, and make fresh decisions about how to proceed next. Then if they have design updates they can flow that information from the office straight out to the machine as well,” says Hester.
Similarly, Topcon’s SiteLink is a site management system that automatically updates work flow, up time, volumes moved etc., which can be shared with supervisors, foremen and operators along with site plan revisions that can be immediately implemented. Fleet diagnostics and management, fuel consumption, idle time, productivity and maintenance are determined down to the level of each machine regardless of the manufacturer.
A case study
Proponents call it the most significant single-highway investment made in Ontario history. By the time the Rt. Hon. Herb Gray Parkway is finished in 2014, trucks travelling Highway 401 from as far away as Montreal will no longer have to wind their way through the city streets and neighbourhoods of Windsor before crossing over to the other side of the Detroit River. A key player in the $1.5-billion parkway project is Ontario-based builder Amico Infrastructures Inc., which will construct approaches to both the brand new international bridge and inspection plaza. The main challenges, says Amico survey manager Scott Rahm, are cuts of up to 12 metres deep and approximately 3 million cubic meters of earth moved, some of it on existing streets and roadways in heavily residential neighbourhoods.
“So we do have a fair number of shovels, dozers and graders. Of those 15 dozers and three graders are equipped with GPS. Without GPS, I don’t know how we could even approach doing this job.”
A case in point: staking. Rahm points out that stakes are still helpful on smaller job sites, but not here where Amico runs about 200 to 250 trucks per day. “If you had stakes they’d be run over five minutes after you put them in.” The close proximity of existing roadways also makes for cramped working conditions for equipment operators. But with all the design information on machine location and blade position on their digital displays “operators don’t need a grade man out there 24/7 telling them every time they make a cut if they’re too deep or not too deep.”
Another challenge, Rahm says, are elevations. Historically, batter boards and the keen eye of a project foreman were the principle means for ensuring proper slopes and curves. That’s less reliable on a job site that features two-dozen bridges and
tunnels, and where equipment operators work from normal ground levels to 12-metres deep. To cut it once and to cut it right, says Rahm, Amico combines GPS technology with Leica’s TS-15 Total Station robotics systems “so that our tolerances are bang on.”
“For the road cuts they’re running at 30 mils both on the sub grade and stone grade. But when we go to do the fine grading with the GPS and the total station it’s not a problem to get to 10 or even five mils.”
Brad Hoey is not convinced. When you grade and pave for airport runways you work to very fine tolerances, says the project manager for Island Asphalt Company in Victoria. GPS will give you that only if you supplement your dozer or grader with conventional laser beam technology. “GPS can tell us elevation differences but it can’t correct within the proper tolerances that we need for paving. It’s not fine enough.” Hoey’s reluctance to use GPS seems to be borne out by the rest of the industry, of which only about 30 to 35 per cent have invested in GPS technology.
Tony Vanneman admits GPS manufacturers have a way to go before the contracting industry fully embraces GPS or even laser-guided technology. What those who don’t use it fail to appreciate, he says, is how far these technologies have come. Today’s laser technologies, for example, are a far cry from the conventional horizontal lasers used 30 years ago and he cites TopCon’s own Laser Zone as an example: a 10-meter high “wall of light” that can cover a job site up to 1,000 feet from the transmitter.
“Anywhere within that laser zone an innumerable number of machines, machine and man rovers can ut
ilize this signal. It
augments or enhances that conventional GPS-only signal and that’s how we’re able to get down to significantly tighter tolerances, whether you’re grading or asphalt or concrete paving.”
Peter Robson and Len Friesen are certainly sold on the technologies. Robson is director of intelligent machine controls for Komatsu, Friesen is a commercial landscaper in Winkler, Man. Friesen had used GPS in landscaping before, but decided to make an even bigger investment last year after he expanded into commercial grading. The result: a JD 200 Excavator and JD 333 Skid Steer equipped with a Topcon GPS system (the first sold in Western Canada) and two JD 650J and 700J dozers with Topcon’s 3D-MC2. This system pairs Topcon’s GX-60 control box, GPS+ antenna,
MC-R3 receiver and sensors with advanced controlling software to provide position updates up to 100 times per second. A costly venture at $150,000 per machine? Sure, says Friesen, “but there’s a cost factor in not being able to do your job as well.”
“If you’re waiting for someone to give you grades and you underfill or over fill you’re going back to do the same job twice.”
A bonus, adds Robson, is a relatively quick return on investment in GPS technologies of “anywhere from 12 to 18 months.” Trimble’s Hester calls that “a good estimate,” but says paving contractors can do even better once their bonuses kick in. “If we’re helping you to achieve the smoothest surface out there so that you can guarantee that you’re going to get your smoothness bonus, you could see a much faster rate of return,” says Robson, all this could push more contractors towards GPS. “I don’t see why in five to six years time it wouldn’t be getting close to everybody using it.”
Greater acceptance is more likely to occur as GPS improves—in particular, says Scott Rahm, in the number of satellite systems available to ensure greater global penetration of satellites signals and greater accuracy. That could mean supplementing the American Navistar and Russian GLONASS systems with the European and Chinese systems. “It tightens the accuracy more and more the longer we go, which is all we can hope for.” Rahm looks forward to a day when GPS will enable contractors to do a job in a single pass “so that you go from the initial cut right down to the millimeter.”
“We’re getting better at that every day. We just hope that continues and we can get better accuracies the further we go.”
David Godkin is a B.C.-based freelance writer and regular contributor to On-Site. Send comments to email@example.com.
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