GPS grade control systems provide earthmoving contractors with a competitive advantage. Just ask Randal Van Rooyen at Van Rooyen Earthmoving.

Based in Woodstock, Ontario, Canada, this family-owned site preparation and mass earthmoving contractor operates roughly 30 pieces of earthmoving equipment. It began using GPS technology three years ago when it purchased three complete systems with base stations, and rovers for the foremen. "We typically take on three grading projects at once and we wanted to have a GPS machine on each of the sites," says Van Rooyen.

Today, in addition to automated systems installed on four dozers, the company has added GPS to a Caterpillar 345C excavator, allowing for an accuracy of +/- 2 in. "We have invested a little more than half a million Canadian," says Van Rooyen.

This investment has made Van Rooyen Earthmoving more competitive. "We probably reduced our staking 75% to 80%," says Van Rooyen. Material management has also improved. "That excavator is cutting to grade right away. The dozers take fewer passes to get to grade. There is no guesswork."

Garrett Excavation, Hot Springs, AR, has also seen productivity jump. The third-generation commercial site development contractor has over 100 pieces of equipment in its fleet. It purchased its first Topcon GPS grade control system in the Spring of 2002. "We now have four complete systems," says Grant Garrett.

Before the GPS, Garrett Excavation did its layout with a total station. "It takes two or three guys and is kind of slow compared to the GPS," says Garrett. "Once we got comfortable using the GPS, we were doing more work with the same amount of guys. We were finishing jobs quicker, and the amount of jobs we were bidding increased. So when we looked back, we did a million and a half more than we did the previous year with the same amount of people."

Garrett Excavation's first GPS job was excavation of a site for a large retail customer. "We paid for the system on that first job," says Garrett. "It takes a good finish operator and makes him a great finish operator - anywhere from 30% to 70% faster, just because he is not waiting on anybody to give him information."

Connections are the weak point
One downside with GPS grade control technology is the system is either working or it isn't. Wiring harnesses tend to be the weak point.

"The cables that connect the various components of the system are the most prone to damage in the 3-D environment," states Murray Lodge, director of sales - construction, Topcon Positioning Systems. "The best way to avoid this is to install the system according to the manufacturer's specifications."

Sukut Construction, Santa Ana, CA, has vast experience with GPS systems. Matt Eklund, GPS program manager, agrees that the biggest reliability issues stem from wiring harnesses. But, he adds, "On the new systems, like the Caterpillar AccuGrade and new Trimble systems, they have redesigned their components so they are more reliable."

Trimble, for instance, eliminated coaxial antenna cables on its newest design. "Each unit contains a GPS (or GPS+Glonass) receiver, antenna and power supply all in a single housing and connects via a CAN bus cable," says Arthur Taylor, 3-D machine control segment manager, Trimble. "This integration eliminates the potential failure point."

Despite such safeguards, problems can crop up with use. "With GPS, you can have a little problem that can intensify if it is not addressed quickly," says Eklund.

Failures can be caused by several issues. "In many grade control systems, there are three general areas prone to failure: GPS coaxial antenna cables; operator displays that are not sealed, leaving them open to water and dust; and general component and sensor survivability and longevity," says Taylor.

However, with proper care, downtime is pretty minimal. "We don't really see any downtime with the systems," says Garrett. "We have had a few instances where guys have pulled the end off a cable or hit the antenna on a building or branch and broke it. Those are more operator errors. With the Topcon system, we can pretty much run all day without any interference."