Policy-makers weigh alternatives to GPS

The public has until Feb. 7 to comment on whether the government should shut down a ground-based long-range radio navigation (Loran) system operated by the Coast Guard or develop an enhanced Loran (eLoran) system that could serve as a critical backup for the Global Positioning System. GPS provides essential electronic navigation and communications timing signals. The Transportation Department recognized GPS’ vulnerability to jamming after the 2001 terrorist attacks, when the Volpe National Transportation Systems Center assessed GPS’ weaknesses and urged the development of a backup system. The Volpe report states that as GPS becomes more embedded in the civil infrastructure, “it becomes a tempting target that could be exploited by individuals, groups or countries hostile to the United States.”President Bush called for developing and maintaining GPS backup systems in a December 2004 policy statement on space-based positioning, timing and navigation systems.Mike Harrison, a consultant, said a recent U.K. decision to invest in an eLoran backup system “sends a very strong signal to the U.S to go ahead” with its own eLoran system. The General Lighthouse Authorities of the United Kingdom and Ireland, an agency that has a role in managing navigation in Europe, said in a report on eLoran that threats to global navigation satellite systems (GNSS) from terrorism or criminal jamming is “credible, real and likely to have significant economic and financial costs.”The report concludes that electronic navigation based on GPS or the European Galileo system is unlikely to be robust or reliable enough to withstand intentional jamming or unintentional interference. It recommends developing eLoran as an “insurance policy against the potentially massive impacts of a terrorist or criminal jamming attack against GNSS.” Harrison said eLoran provides a better backup than a jury-rigged set of alternative GPS backups, such as distance measuring equipment, very-high-frequency omnidirectional range stations and runway instrument landing systems, which would require the Federal Aviation Administration to retain aging ground-based infrastructure.Tom O’Brian, chief of the Time and Frequency Division at the National Institute of Standards and Technology, said eLoran could provide a good and credible GPS backup.Despite strong endorsements, Loran and eLoran have not gained favor at DOT or the Coast Guard. The Coast Guard has spent $160 million to modernize Loran since 1997, after prodding from lawmakers. DOT had received 360 public comments on the future of eLoran as of last week. A majority of the comments were in favor of continuing to operate Loran and develop eLoran.  Military jamming tests conducted near the China Lake Naval Air Warfare Center in California disrupt GPS signals for hundreds of miles, said David Lister, a private pilot, who submitted a comment on DOT’s Loran Web site. Lister wrote that he experiences signal loss in one of about 10 or 20 flights, “which is much too frequent for GPS to be used as a sole means of navigation.”