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" Satellite-based navigation has become a ubiquitous tool for business, military and personal use. The downside is that any disruption in the Global Positioning System could wreak havoc down on Earth. This year, the Department of Homeland Security decided that a 30-year-old navigation system used by mariners will be upgraded to back up GPS. The decision preserves the Long-Range Aids to Navigation (LORAN) network, which has been teetering on the verge of forced retirement since the 1980s, according to the Coast Guard&amp;#039;s Navigation Center. The backbone of LORAN is a network of transmission stations, many located in remote regions, staffed with Coast Guard personnel, and equipped with antennas as tall as 900 ft. The 2009 DHS budget allocates $34.5 million for the Coast Guard to start upgrading the LORAN system with modern electronics and solid-state transmitters. Users of the enhanced system, called eLORAN, will acquire and track signals from ground stations in much the same way they triangulate signals from multiple satellite feeds. LORAN also adds a data channel that can handle more detailed information. The system won&amp;#039;t just wait for GPS to fail: eLORAN stations will continually transmit time-keeping data needed for navigation and warnings about coming disruptions. Why GPS Needs a Backup Plan Intentional Jamming  Threat: GPS signals use low-powered, high-frequency signals that are easy to block. eLORAN Fix: Uses high-powered transmitters that send stronger signals requiring more power to disrupt. Environmental Interference Threat: Signals from GPS sats need to be in the line of sight of receivers and are blocked by metal, mountains and reinforced concrete. eLORAN Fix: Terrestrial signals bend around the Earth&amp;#039;s curvature and can penetrate urban canyons and dense foliage. Cosmic Radiation Threat: Unusually large solar flares can produce radio bursts over the same frequency bands as GPS satellite transmissions. eLORAN Fix: Cosmic radio waves cannot penetrate the ionosphere, so LORAN signals are immune to interference.  Antisatellite Weapons Threat: Future ground-based missiles could target and knock out GPS satellites. eLORAN Fix:Ground stations can be more easily guarded from attacks, including those by missiles.  RELATED STORIES * COMPARISON TEST: 5 New GPS on the Road &amp;amp;amp; in the Lab  * GLENN DERENE: GPS Manufacturers Scared of iPhone 2.0  * PLUS: Inside the FAA&amp;#039;s GPS Fix to Bust Airport Gridlock   LORAN Station, Attu, Alaska: This is the view from the 600-ft. LORAN tower. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/technology/gadgets/a12108/4266972/>