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  • Jamming? U Tex Can Do It Anyhow
    Posted by Bill Sweetman 10:37 AM on Jul 02, 2012

    Reports of the death of the Global Positioning System may be premature, but that is not to say that the system is altogether healthy.

    The University of Texas' Austin campus did win some coverage last week with a report that its student team had succeeded in spoofing the GPS on an unmanned air vehicle at a range of 1 km and causing it to change position, during a demonstration at the White Sands missile range in New Mexico. The team had been invited to demonstrate the technology by the Department of Homeland Security.

    DHS, however, was quick to quash reports that it had "dared" the team, led by Cockrell School of Engineering assistant professor Todd Humphreys, to perform the experiment, and that the team had "hijacked" a DHS drone. DHS provided an environment where the experiment could be conducted without high collateral risk, and the target was a quadrotor bought on the commercial market.

    One important distinction is that the quadrotor's GPS was its sole source of position information. Although we talk about UAVs and missiles being "GPS-guided" their primary navigation system is usually inertial: the job of the GPS is to correct drift, and the algorithms that blend the two will disregard a blorp in the GPS if it disagrees profoundly with the triplicate inertial sensors.

    Additionally, professional-grade UAVs have directional GPS antennas with far higher gain in the upward direction -- which means that the spoofer, radiating from the ground, has to overpower the real GPS signal by orders of magnitude.

    However, this doesn't mean that GPS is out of the woods. DHS and other authorities are becoming increasingly concerned about both GPS spoofing and jamming, particularly closer to the ground. The jamming issue has arisen because of the proliferation of GPS tracking devices that can be used overtly and legitimately (by vehicle fleet operators, for instance) or covertly (by suspicious spouses, or stalkers).

    According to the golden rule of electronic warfare, this has led to a counter-move -- the supply of cheap (and quite illegal) GPS jammers. The US government recently attempted to clamp down on the import and sale of these devices, with no apparent effect except that they cost less than when I last looked at them a year and a half ago.  

    One result may be increased interest in "GPS 2.0" -- the fusion of GPS with higher-powered and hence more robust terrestrial systems. A pioneer in this area, Australia's Locata Corporation, has deployed patented positioning technology to the mining industry in partnership with Leica Geosystems and has provided a test system for the USAF at White Sands -- where it is used as a baseline for GPS interference tests. Locata has just announced that it is opening its doors to partners in other industries, including aerospace and defense.

    Tags: ar99, gps, jamming

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