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Private GNSS Network Covers Five Midwestern States

Wed September 02, 2009 - Midwest Edition
Construction Equipment Guide

“There’s nothing magical, or even particularly difficult, about putting together a network of GPS reference stations to support surveyors. All of the major players support that kind of networking. What makes PSC Net different is the fact that it was designed from the start as a machine control network, and that’s a horse of a very different color,” said Jerry Bickner.

Bickner is intimately acquainted with the difference. He’s the president of Carol Stream, Ill.-based Positioning Solutions Inc., developer and operator of PSC Net, one of the few private machine control networks in the world.

“We serve both surveyors and contractors,” Bickner said, “and they’re all interested in the practical advantages of so-called Global Networked Satellite Systems [GNSS] that link a number of base stations together via a computer network. Anyone working inside the network area can literally walk around with a rover on a pole and get centimeter-accurate observations without the need to set up a base station. The productivity advantages are obvious.”

Probably the best known GNSSsystem today is the Albuquerque Real Time GNSS Network, or ARTGN, but there are more than 35 others of various sizes in the United States today. They’re also operating in Japan, China, Europe and Dubai.

“What they all have in common is a heavy focus on the survey side of the business,” Bickner noted. “Frankly, that’s a lot easier to do than machine control.

“Every network has built-in time lags between the input and output, it’s called ’latency’. You’ve got to gather the data, move it to a central processing location, process it, and then deliver it to the end user. All of that takes time, even at the speed of modern electronics.

“A surveyor can afford to wait a few seconds for a correction while all of that happens. A dozer or grader can’t. That’s one of several reasons why machine control networks are so much harder to design, build, and operate.”

Positioning Solutions serves customers in five states — Illinois, Indiana, Michigan, Missouri, and Wisconsin. Its initial GNSS-based machine control network application was developed to serve the Indianapolis market, and the Indianapolis office continues to be the central processing hub for the now greatly expanded PSC Net.

“We started in Indianapolis about three years ago because we had both a strong market presence and a strong technical base there,” Bicker said. “We added Chicago next but kept the actual network computers and processing centralized in Indianapolis to take maximum advantage of the experience base there.”

Positioning Solutions is a Topcon distributor, a fact that gave them several advantages in developing PSC Net, according to Bickner.

“ARTGN is Topcon-based,” Bickner explained. “So there was a wealth of practical experience available to us when we started designing PSC Net. In many cases, a simple phone call got us answers to questions that might have taken months to resolve if we had to start from scratch.”

PSC Net started in 2005 with half a dozen Topcon reference stations. That has grown to more than 40 today, with four more being added each month on average. Within the next three years it plans to cover all of the major metropolitan areas in the five states served by Positioning Solutions.

“We are a very customer driven company, and our customers wanted something more than a simple GNSS network. So, we designed PSC Net from the beginning to be a machine control network, and today it’s the only one available in the Midwest,” Bickner said.

The key to a successful machine control network is latency reduction. Latency itself is a physical phenomenon, and short of repealing the laws of physics there is no way to eliminate it. But, good network design can minimize latency, and good software design can compensate for it. Making that happen, however, requires both network and software engineers to focus on latency reduction as a primary goal from the beginning.

Topcon 3D machine controls were designed for networking from the beginning.

One interesting aspect of PSC Net is the fact that most of the reference stations in it are owned by individual customers. Positioning Solutions supplies the system engineering, computer processing power, and networking technology to integrate them into PSC Net, but any PSC Net subscriber can access any PSC Net reference station and use it as if it was its own.

PSC Net uses the Internet as its communication infrastructure, which presents a unique set of challenges in locating and connecting reference stations.

“Physically mounting the antennas is the simple part,” Bickner noted. “Getting everything linked together on the Internet can be a bit more challenging. We need a constant connection either via landline or the cellular system ,which isn’t always easy.

“You might find company ’Z’ in the perfect location to fill in a gap in the network. But, when you get there the building is wrong, or the sight lines are blocked, or there are some other technical issues.

“And then there are firewalls and individual system quirks to be accommodated. In the end, every connection is unique, and every connection requires a unique solution.”

Because PSC Net uses Topcon reference stations exclusively, satellite availability is not one of the problems Positioning Solutions has to deal with. Like all Topcon receivers, the reference stations used in PSC Net can use signals from the U.S. GPS, the Russian Glonass, and the soon to be available European Galileo and Chinese Compass/Beidou satellite constellations.

Topcon’s “Multiple Constellation” capability means there is virtually never a time when the receivers are not in contact with satellites of one or more constellations. That virtually eliminates “no signal” downtime, and minimizes potential “blind spots” on the work site. It also makes it much easier for Positioning Solutions to locate network reference stations, according to Bickner.

“The rapid growth of PSC Net shows how valuable our customers think it is,” Bickner said. “But, like any advanced technology there’s a learning curve attached. Once the network was available they needed training to help them use it.”

Positioning Solutions responded by establishing its own university devoted exclusively to helping its customers utilize the capabilities of PSC Net and GPS technology to maximize its competitive advantage. In less than two years, PSC University has trained several hundred students representing more than 60 different companies. More than 90 percent of the companies participating have returned for multiple classes.

“PSC University has been so well received,” Bickner said, “that we are now well along in developing Phase Two and Phase Three level classes. Not only will we be offering more classes and more topics, we will also be taking PSC University on the road to customer locations and other venues.”

With more than three years of hands-on experience in implementing a machine control GNSS network, Bickner has several words of advice for others who might be contemplating similar projects.

First, he said, “Know what the end looks like, this isn’t something that can be done ad hoc.”

Bases, for example, need to be properly located and aligned for network operation.

“People tend to believe that a station actually is where it says it is,” Bickner said. “But, that’s not always true. There are always errors, and the network has to be able to compensate for them. We have even found state monuments that aren’t correct.”

Base lines also need to be kept as short as possible.

“Competitive networks tend to have much longer baselines than PSC Net. As one gets further from the base, the errors increase, it’s just that simple.”

Bickner also noted that vertical accuracy is critical to a machine control network.

“Survey-oriented systems tend not to focus on vertical accuracy,” he said. “We have seen errors as great as 6 to 8 feet in the vertical plane. Worse yet, those errors are not consistent so you can’t compensate for them. That’s simply not acceptable for a machine control application.”

Positioning Solutions routinely collects several weeks worth of data from every new reference station before it’s added to the network.

“Errors are like latency in the fact that both are inevitable,” Bickner said. “But consistent errors, like latency, can be compensated for by good network design and good software. We make a lot of corrections in the server to ensure the greatest possible accuracy in the data we deliver to our customers.

“If we don’t have full confidence in a reference station, we won’t attach it to PSC Net, no matter how badly we may need that location. As far as we’re concerned, no data is infinitely preferable to bad data — especially when you’re using it to control a bulldozer.”

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