Sandia researchers Jonathan Van Houten (left) and Jeremy Giron
A Combination of Sensors Enhances Detection
February / March 2007
Volume 5 Number 1
The integration of off-the-shelf sensors with much more robust proprietary sensor technology developed at Sandia National Laboratories may result in cost-effective yet highly effective security sensing for both national security and private defense.
Rather than try to reinvent the wheel when working on unattended ground sensor projects for internal projects such as Sensor Dart, Target Acquisition, Location, Observation and Neutralization (TALON), and Virtual Perimeter System, researchers at Sandia's Embedded Sensor System Department instead chose to place their own sophisticated sensor at the hub of the proverbial wheel and use commercially available sensors arrayed as if they were four spokes of the wheel.
The four quadrants of smaller sensors would serve as the first line of electronic sentries that would alert the much larger central sensor to any intrusion by man, beast or machine.
"This particular effort was exploring what capabilities could we expect from a system that combined inexpensive commercially available sensors with our more expensive custom sensors," said Mark D. Ladd, manager of Sandia's embedded sensor systems department. "The project did demonstrate a new capability for a reasonable cost per square meter target." The technology was developed quickly in the final four months of the 2006 fiscal year after the researchers were presented with a specific challenge. Sandia's Laboratory Directed Research and Development program provided $75,000 to fund the project. One of the first tests of the sensor network was at the Albuquerque zoo, where the sensors were shown to be successful at distinguishing humans from the myriad of fauna at the facility.
Casting a Wider Net
At the heart of the array is Sandia's proprietary sensor that uses digital signal processing, video monitoring, global positioning system tracking, and local and long-range radios to perform sophisticated analysis of any intrusion into a secure location. When a breach is detected, the unattended ground sensor (UGS) sends a radio alert that alerts guards and pinpoints the position of the intrusion.
But deploying only such high-powered sensing technology would be prohibitively expensive in many applications. The Sandia team, headed by Hung Nguyen, sought to maximize cost-effectiveness by augmenting the reach of the primary UGS with commercial sensors made by Crossbow Technology Inc. of San Jose, Calif. The Crossbow sensors were modified with new control algorithms as well as nominal structural changes. The sensors effectively serve as miniature seismographs using four-inch spikes embedded into the ground. The Crossbow sensors can be powered by battery or solar panel. When a person, animal or vehicle moves within the range of the small sensor, it sends a radio signal to the Sandia sensor and alerts it that an in-depth investigation is needed at a specific location.
By using an ad-hoc network that permits hopping of the radio signal, the commercial sensors can significantly increase the detection range of the total system with a minimum of false alarms. Multiple UGS networks could be strategically arrayed to sense movement across a wide and topographically diverse landscape.
"Some analysis would be required to provide the maximum area of coverage, but we believe that the technology can support most areas of interest our customers would have," said Ladd. "From our standpoint, it's the cost per square meter and the time it takes to propagate messages through the network that are the driving factors, given the system generates useful data."
When the Sandia sensor alerts guards in prototype form, it sends a signal to a stand-alone computer running a Google Earth user display even though the computer is not connected to the internet. "We used Google Earth since we were able to develop very quickly a user display capability depicting the locations, status and alarm states of the sensors," Ladd says. "Most customers would require the sensor network to interface directly with their existing display software."
Commercialization Efforts
Asked whether a perpetrator might be able to jam the radio signals of the sensor network, Ladd conceded that more work will be needed to ensure that signals are delivered securely.
"A threat assessment has not been performed on this technology, but yes, for the sensors, this would be an issue," he said. "The purpose of this study was to assess whether or not useful intrusion detection information could be provided by the sensor network in a timely manner. This represents the first of a couple of steps needed before the system could be deployed at a functional site."
The network will be further studied as part of Sandia's intrusion detection efforts and commercialization to the private sector is anticipated. "We have been approached by some vendors with interest in commercializing Sandia's ground sensing technology but we haven't reached any formal agreements, though that is a desired goal of ours," Ladd says.
G. Jeffrey Hoch reports on Sandia for Innovation.
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