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A Little Off the Top

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With help from millimeter-grade GPS, Redland Corp. has become a go-to source for ultra-fine grading.

Hands down, the reason most-often cited for a company’s reluctance to move toward a GNSS-based capital equipment purchase is cost. Despite steadily declining prices for machine control systems, GNSS base/receiver solutions, etc., the expense — and the uncertainty of how long it will take for the technology to pay for itself — often remains a stumbling block for many. Not so for the Redland Company which not only embraced GNSS long ago and currently employs it in almost every facet of its operation, it has also recognized the lucrative potential it can hold when offered as a service. On a unique 475-acre Florida Department of Transportation (FDOT) project, the company used millimeter-grade GNSS on a GOMACO 9500 trimmer to final grade a 2.25 mile oval track, saving months over traditional string line grading. And that was just one of an almost continuous string of such opportunities into which the company has tapped. For them, the solution has gone from what it first saw as a necessary expense to what it never expected to see: an entirely new profit center.

Drivers’ Test

The full scope of the project referenced above involves construction of a facility that FDOT calls “a continuously evolving, nationally recognized center for the development of innovative transportation technology solutions.” In essence, it will be a proving ground for new technologies — with a focus on autonomous vehicles — as they evolve. When complete, the center will offer everything from an environmental test chamber which will simulate differing weather conditions, to an area where pick-ups and drop-offs can be replicated, and much more. However, according to Walt Thomas, Redland’s division superintendent for grading/trimming operations, this  200+ acre “infield of dreams” is literally framed by a precision-graded 2.25 mile oval track.

“The SunTrax project is being headed up by Bergeron Land Development (Davie, Fla.), which, as the GC, did all the preliminary work on the track,” he said. “The oval is designed to handle vehicles at a 70 mph speed, much the same as actual turnpike travel. Because FDOT had some very strict tolerances on the track surface itself, the grade had to be extremely precise. So when we got out here, all the rough grading had been completed and we were brought in to prepare it for the asphalt course.”

It’s important to note that Florida differs from other states — particularly those that deal with colder temperatures — in their approach to highway paving. While such states can have up to 8-inches of aggregate base covered by an equal thickness of asphalt or concrete, such is not the case in the Sunshine State, said Thomas. “Here, the base is the key component; most of our major highways are topped with only 3.75 inches of asphalt or concrete,” he said. “So the demands for accuracy on the 8” lime rock base — with a 95% relative compaction — were strict. On this job, what we might lack in depth, we are more than making up for in precision.”

"Because FDOT had some very strict tolerances on the track surface itself, the grade had to be extremely precise. So when we got out here, all the rough grading had been completed and we were brought in to prepare it for the asphalt course.”

- Walt Thomas, Redland’s division superintendent for grading/trimming operations

Neatly Trimmed

Redland Company’s tool of choice for ultra-fine grading is a trimmer/placer which offers a number of advantages over a motor grader for that type of work, including an ability to resist “floating” over higher-density material or cutting into material that is lower in density. To maintain grade, trimmers are typically used in conjunction with a string line which, while effective and accurate, is also labor-intensive, time-consuming and challenging.

“Traditionally, we would have been given grade control and we would set pins and string line — similar to what we do with a curb machine — dial in our cross slopes, and so on,” said Thomas. “In fact, we have six other three-track CMi trimmers in which we still do things that way. However, the size of this project, coupled with a huge amount of the grade breaks and a need to get things wrapped up quickly, more or less dictated for us how SunTrax should be done. We’ve had Millimeter GPS from Topcon Positioning Systems (Livermore, Calif.), on this GOMACO 9500 for about two years now and have gotten tremendous results with it — we knew that, for here, it was the only viable trimming approach.”

Redland’s Millimeter GPS is a GNSS-based solution that uses a series of tripod-mounted Topcon LZ-T5 laser transmitters, placed at an established reference point, to generate a 33 foot high Laser Zone signal. That signal is accessed by the receiver on the trimmer and used to determine elevation, set the necessary depth of the trimmerhead, and maintain the required tolerances.

“For most of the project, two lasers suited us just fine,” said Thomas.  However, for the curved sections of the oval track, we linked four of the LZ-T5s together and were able to get our millimeter-grade solution throughout the curve. Between those, the number of grade breaks and the overall size of the job (we also did a turnaround loop that will be used for testing larger autonomous vehicles like semi-trailers), this could have been a real challenge using string line. Instead, aside from some weather delays, it went off like clockwork. Trimming anywhere from 1” to 2” of material, we were averaging rates of about 800 sq. yds. per day — and the accuracies have consistently been dead on.”

Many Happy Returns

Obviously a company which commits to any major purchase — Millimeter GPS included —  is literally banking on it providing a decent return on investment each time it is used. Redland has not been disappointed in that regard at all — the machine running the millimeter grade system is steadily in demand by many of the area’s premier grading contractors.

“For us, it has paid nice dividends,” said Thomas. “Our ability to come onto a jobsite and get grade to within .02, do it consistently and do it without setting up a single pin or running any string line, has made us very popular from here to North Carolina. When a contractor has a flexible schedule, they can (and do) use a motor grader or two to get to final grade. But if they are in a situation where they want to accelerate their job by as much as three or four months, that’s when they give us a call.”

Comfort in 3D

All of the GNSS solutions Redland Company used at the SunTrax site, including the 3D millimeter system, the Topcon HiPerV base and rover, laser units and FC-5000 controllers, were purchased through Lengemann Corporation (Altoona, Fla.) which, according to Thomas, has been outstanding in both availability and support.

“Because we’ve been using GPS for a while now, we’ve got quite a history with Roger Croft and the Lengemann team and it’s been great,” he said. “They are big enough to have everything we could possibly need, yet not too big that they forget who we are. Even though I find Topcon’s products to be far more intuitive than anything else available today, we still occasionally hit a point where we need help and they are always there for us.”

Redland’s use of the 3D system on their trimmer harkens back to their overall belief in GNSS as a whole, a move that began with machine control on dozers and motor graders and grew from there.

“That technology quickly became almost the only way we did things,” he said.  “So when we started getting more and more grading work that demanded speed and a high level of accuracy, we turned to Lengemann who introduced us to Millimeter GPS. It’s been great for our own operation and a powerful solution to offer as a subcontractor. We are getting to a point here in Florida where having a 3D capability is almost a prerequisite for bidding many jobs. No problem, we are already there.”

The SunTrax facility is being jointly developed by Florida's Turnpike Enterprise (FTE), Florida Polytechnic University, and industry partners. The cutting-edge facility, which will offer unique opportunities for testing emerging transportation technologies in safe and controlled environments, is being touted as the only high-speed autonomous vehicle testing facility in the southeastern U.S.