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Blade control: You'll be surprised what contractors are saying. 
By Penelope Grenoble O'Malley GPS Keeps the Nation's Oldest Contracting Company Up With the Youngsters Todd Gokey is project engineer for Barrett Paving Materials Inc., the oldest contractor in the nation, established in 1864. Today the Syracuse, NY, division he works for does airport and highway reconstruction work, and for the past three months Gokey has been working with Leica GPS indicate systems on two dozers and an automatic system on a Cat G12 motor grader. Typically, operators are expected to meet tolerances of plus or minus 6 millimeters-one-quarter of an inch. "One of our motivations for GPS," says Gokey, "was that New York State DOT [Department of Transportation] has set up a spider [RTK] network with their own base stations. Their intent is that their inspectors will use rovers, and they have announced they're going to change the spec books to accommodate automated machinery. The specifications on a recent job included that the contractor had to buy the state a base station and a couple of rovers. "The way we're set up now, we use the rover for all our survey work, including drainage structures, pipes, and the center line for the pavers. The excavator does the bulk of the work, and the dozer comes behind and gets the fine grade done. Leica just came out with a 3D system for excavators, and I'm looking into that. If we had GPS on the excavator, the operator would know exactly what he's digging and where. And with a system on an excavator, the dozer and excavator would almost be a standalone crew." Getting Help From the Pros In Richfield, VA, Liefeld Contracting Inc. is using a private RTK set up for Leica equipment users by Loyola Spatial Systems, which eliminates the need to set up a base station. Permanent reference stations send data to an IP address on the Internet. At the rover end, customers have a cellular modem to receive the real-time data. "There's a lot of paraphernalia associated with GPS equipment," says Kenny Liefeld, "so when you can go into the job, put the computer into the cab, hit grade, and go to work, it's awesome." Liefeld Contracting Inc. does heavy highway work, commercial sitework, and an occasional subdivision. Currently it has three machines out of an inventory of 130 that are GPS-equipped. These include automated systems on a Caterpillar D 6N dozer and a 143 Caterpillar motor grader and an indicate system on a John Deere 450 excavator. They've been using the system on the dozer for two years, a year on the grader, and only a few months on the excavator. A rover rough stakes the jobs. "Before GPS," says Liefeld, "we used lasers. And in fact, the motor grader and the dozer and the excavator all have 2D systems. I use the 2D to calculate where the blade is and the GPS to tell the machine where it's at on the job site. We'll rough grade a building pad with GPS, which is where I think it really shines. We move the dirt only once and can get within a couple of tenths versus a couple of feet. Then we set the laser up. "For something like a retention basin, we use the excavator to cut it out as close to grade as we can. Then we follow behind with the automated dozer, which clips it and gets it on grade. Then we use the motor grader to get to fine grade. "If it was up to me, if money was no object and things were going well enough that we felt comfortable that we would go headfirst into this, we would probably have at least one pan [scraper] indicator system and probably use a D8 with an indicator system to rough a cut, and a D6 would run the fill. That way, the job is full of GPS and everybody knows what's going on." One of the factors that would make Liefeld feel more comfortable is having a good model to go by. "When you have a good model, everybody is working off the same information, but the biggest hurdle is getting the digital file, creating the model in a timely fashion, and getting it out in the field. Machines do what they're told to do very well. If you tell a machine to do something wrong, it will do it exactly wrong." At Mathiowetz Construction, Brian Mathiowetz echoes a lot of contractors about models and file conversion. "The onsite stuff is simple. The guys out there have got that figured out. Set your base station up and get going. The difficult part of working with GPS is when the file they give us is loaded with errors and we have to start cleaning it before we can work with it. "You ask the engineer if he looked at the whole file after he tweaked the controls in one corner. Did he see how what he did impacted the other parking lot? And he won't have done that. We get a plan on Monday, and then we might get a different one on Tuesday and a different one on Friday. How do I know what's changed? We're probably going to have to hire more people to check plans, which is effectively working against the cost savings these systems are supposed to generate." Journalist Penelope Grenoble O'Malley is a frequent contributor to environmental publications. GEC - November/December 2006 |
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