Exposing Buried Danger: Field Tests Advance Seismic Landmine Detection System
The system uses high-frequency seismic waves to displace soil and objects in it slightly (less than one ten-thousandth of an inch). A non-contacting radar sensor then measures the results, creating a visual representation of the displacement that reveals the buried mines.
This seismic-wave system may prove itself more reliable than existing electromagnetic-wave techniques used in metal detectors and ground-penetrating radars (GPR). Although metal detectors and GPRs can locate mines successfully, they have more trouble locating the small, plastic anti-personnel mines that have become more prevalent. Metal detectors and GPRs can also be confused by ground clutter -- rocks, sticks or scraps of metal - sometimes resulting in many false alarms.
Yet because plastic mines have very different mechanical properties from soil and ground clutter, the seismic waves are capable of detecting and distinguishing these mines from common ground clutter. Researchers have demonstrated this advantage in laboratory and limited field tests.
"When a wave hits a land mine, resonance builds over the top of the mine, triggering a vibration which is bigger than the wave that excited it -- and the vibration persists longer," said Waymond R. Scott Jr., a professor in Georgia Tech's School of Electrical and Computer Engineering and principal investigator on the project.
Sponsored by the U.S. Office of Naval Research, the U.S. Army Research Office and the U.S. Army Night Vision & Electronic Sensors Systems Directorate, the mine-detection project involves researchers from various departments at Georgia Tech. This multidisciplinary team started work in 1997 with computer modeling and lab experiments. Field testing began in fall 2001, and during the past two years, the researchers have conducted tests at six sites.
In November 2002, the researchers traveled to a government testing facility in a temperate climate where they detected six different anti-tank and anti-personnel mines. "Our results there were comparable to what we saw in the lab, which was very significant. That was a big hurdle for us," Scott said.
Field tests at government facilities give the researchers greater credibility because conditions are more realistic, and they can compare results to data from other research teams. What's more, the mines at government test sites have been buried for several years, which complicates detection.
"It's much easier to detect a mine that's been buried recently because you've disturbed the soil," said George McCall, a senior research engineer in the Georgia Tech Research Institute's Electro-Optics, Environment and Materials Laboratory. "After a land mine has been in the ground for a while, the soil becomes weathered and more compact. This makes it harder to find, so it's a better test for our detection system."