GPS Provides Efficiency

By Aram Kalousdian, Editor | September 28, 2010

A new 110-acre retail development called Hartland Towne Square is under construction on the northeast side of US-23 and M-59 in Hartland Township. The development project includes two big box stores and the relocation of a sewage treatment facility and Hartland Road.

Site Development, Inc., of Madison Heights, is doing the initial earth balancing for the project. Rockford Construction, of Grand Rapids, is the construction manager for the project. The property is being developed by Ramco-Gershenson, Inc.

Site Development, Inc. began working on the project last winter and will continue working on it through at least this summer.

Site Development, Inc. is using a Cat 345D LC excavator retrofitted with a Trimble global positioning system (GPS) on it.

"We wanted to demonstrate that an excavator GPS system could be just as beneficial to Site Development as the tractor systems they were familiar with. So, we partnered with Site Precision Inc., of Grand Rapids, to install a Trimble GPS system on that excavator," said Jay Frost, director of Machine Control Grading and Technology and Productivity Solutions at Michigan CAT.

Site Development is using the Trimble GCS900 system. It uses the MS990 GPS receiver and features the CB430 display and SNR900 radio.

"The excavator has the design displayed right in front of the operator, and they know precisely where the edges are of the curb, trench, pond, ditch, or whatever they are digging. They know where the horizontal edges are and they know the vertical depth that they need to go or the slope that they need to have. So, they get to see all of that. The only difference between a dozer or motor grader and an excavator is that on an excavator system, we do not put grade automation into the hydraulic system," Frost said.

"The two ways that these GPS systems are used are either indicate mode or automatic mode. Indicate means that it tells you where the grade is and you must manually follow it. Automatic means that the onboard computer adjusts the blade of the machine to match the grade. We do not automatically match the grade on an excavator. You are always in control of the machine. You can always override an automatic system, but we don't put an automatic system on anything that digs below ground."

"We have dozers with GPS units on the site. There are several storm water detention ponds to the north that we were doing some final shaping work on. We had some revisions to the plan that came out after we started the work. We went so far with the dozers and then we thought that this would be a good chance to test the Cat 345D LC with the GPS system," John Houser, chief engineer and GPS manager for Site Development, Inc., said.

"The excavator bucket and boom is not automated. We can make the dozer blade automated so that it follows the design surface that is created for it. So, originally, we used the excavator at that pond to do the final shaping. Between looking at the bucket and viewing the screen, the operator can see the elevation that the teeth of the bucket need to be in order to fine grade the slope of the detention basin. There is no need for a grade checker, and the operator doesn't need to look at grade stakes. So, there are a number of efficiencies with GPS, including time and money."

Andy Dryer, the equipment operator on the Cat 345D LC, is new to GPS. "This system was very easy to learn. Without GPS, I would spend as much as half of my time waiting for the grade to be checked. Now, we just keep working," Dryer said.

The excavator was also used for a 15-foot cut in the center of the project. The excavator was able to cut to grade without over cutting or cutting too little. "That speaks to the efficiency that we've found. It eliminates the need for another grade checker to be there with the excavator operator or for the excavator operator to try and look at grade stakes that a surveyor might have staked," Houser said.

"When you get to the point where you're within a couple of feet, you know exactly where the bottom is. You're not going to overcut it. If you overcut it, then you have to place and compact structural backfill. So, you never want to overcut because you're wasting time by introducing an unnecessary backfill operation. If you don't cut enough, then you need a dozer to help clean it up. GPS on the excavator minimizes the need for the dozer."

Site Development is also using a Cat D6R LGP tractor with a Cat AccuGrade GPS system and a John Deere 750J LGP dozer with a Trimble GPS system at the development.

Frost explained that contractors see GPS as their ticket to making money in a down economy. "They can do their work more efficiently and they can make money," he said.


Project: Hartland Towne Square in Hartland Township

Prime contractor: Rockford Construction, of Grand Rapids

Earth balancing subcontractor: Site Development, Inc., of Madison Heights