Global Positioning Technology
May Help Pave Way For Better Roads

12-23-97
University Park, Pa. - For drivers, nothing is more joyful than cruising along a smooth, brand-new stretch of road. But making sure the roadway surface can handle the stresses of traffic and the environment has always been a challenge to contractors. Ensuring proper compaction of roadway materials as they build new roads is an ongoing concern for construction crews.

"If you don't roll over the road enough times, you get low density. If you roll over it too many times, you further crush the aggregates, again causing low density," said Amr A. Oloufa, assistant professor of architectural engineering. Oloufa said a lack of proper density may cause potholes, create lower speed limits, or even shut down a road completely.

The problem that has plagued contractors is that no accurate method exists to make sure a road has the proper compaction throughout. Inspectors can check compaction using nuclear guages, but on the average, only one sample is drawn for every 1,000 feet of road and that method requires special training.

"A lot of money is spent to make sure it's done right," said Randolph Thomas, professor of civil engineering. "Despite the money that's spent, contractors still don't know for sure it's done right."

But a research project started three years ago by Oloufa and Thomas may change all that. The project, a collaboration with David C. Swanson, a research associate at the Applied Research Lab, and sponsored by Ingersoll-Rand and the Ben Franklin Partnership, uses the Global Positioning System (GPS) to monitor compacting on a road surface. Owned by the U.S. Department of Defense, the GPS is a network of 24 satellites and ground monitoring and control stations. Using the signals from these orbiting satellites and a GPS receiver, a person can pinpoint his location anywhere on the planet.

The researchers devised specialized software that processes GPS data and gives compactor operators real-time information as they roll over roadways. Using standard GPS equipment mounted on the compactor, information about the position of the moving compactor is relayed to a computer that translates the data into color codes. The color codes correspond to the compactor's position and changes in colors denote how many passes the machine has made. The information is relayed to a computer screen for the compactor driver, who can make crucial real-time adjustments as he works on the road.

"As you're driving the compactor, it tells you if you're on the right spot or not, or if it's compact enough," Oloufa said.

The team spent much time in the field gathering data for vibrations, positioning, and other operating variables. When the project is completed, an integrated system of sensors for positioning, temperature, humidity, and vibration will be developed.

Keeping an eye on costs, the researchers turned to off-the-shelf equipment and sensors to create their system. Outfitting a compactor with the researchers' GPS setup will cost less than $9,000.

"A compactor costs $100,000," he said. "So you can't put $85,000 of equipment on it and expect it to sell." Oloufa said the team hopes to have the system available for commercial use by late 1998.

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Dr. Oloufa can be reached at (814) 863-2080 or by e-mail at aao1@psu.edu.