How vulnerable is GPS?

There’s a heavy reliance on global positioning technology nowadays, but it’s not just smart phones and in-car sat nav systems. Most areas of industry, transport and telecoms depend on GPS in some form and there’s an increased focus on what will happen in the event of complete failure. According to the BBC website, technology that was developed during World War II is now a contender as a backup to GPS, should the unthinkable happen.

GPS technology employs relatively weak transmission signals, so it is susceptible to the radio noise broadcast by the sun during solar storms, as well as to intentional jamming.

The BBC article quotes Professor David Last from the UK’s Royal Institute of Navigation as saying "A little bit of power from a jammer on the frequency used by GPS close to your receiver can deafen it, and it won’t be able to hear the GPS signals. For example, jamming is a real issue in Korea. There have now been three occasions when the North Koreans have transmitted high-powered jamming in South Korea".

In a less sinister, yet potentially more commonplace scenario, the systems are easily knocked offline during solar flares as GPS positions are prone to wobble. Disturbance to signals can effectively result in GPS capability being lost to the entire sunlit side of the earth.

Global navigation satellite systems (GNSS) are employed by many critical instruments on ships, including the gyrocompass which controls the steering, through to the radar and the dynamic positioning instrument. Electronic charts, timekeeping devices and even the onboard entertainment system rely on GPS, so it’s easy to see why there is a requirement for a reliable alternative.

Britain’s General Lighthouse Authorities (GLA) aim to combat vulnerability through implementation of the e-Loran system, which it has installed in seven British ports. The Long Range Navigation (Loran) system was developed by the United States to guide Navy warships in the Pacific during World War II. Post-war, it was renamed Loran-C and became the universally accepted marine navigation system, prior to the development of GPS.

The technology has again been renamed - now e-Loran - and utilises ground-based radio stations to transmit long-range radio waves, which are extremely strong relative to GPS transmissions. In the case of current shipping trials, vessels are being fitted with dual e-Loran and GPS receivers, which will automatically swap to the alternate technology in the event of interference, jamming or satellite failure.

Prof Last suggests that it could be a suitable technology for land-based GPS systems and not limited to shipping. According to the article, however, as the UK brings the e-Loran in, other countries are in the process of phasing it out, suggesting that it will not be the globally accepted GPS backup.

Perhaps the answer is to be found at a quantum level. NewScientist published an article earlier this year that suggests accelerometers based on super-cooled atoms will be capable of tracking positioning with extreme precision; around 1000 times more accurate than currently available methods. The technology is known as ‘quantum positioning’ and is being tested in submarine navigation applications, given that GPS technology does not work under water.

According to NewScientist, the UK’s Defence Science and Technology Laboratory (DSTL) is building on the discovery that “lasers can trap and cool a cloud of atoms placed in a vacuum to a fraction of a degree above absolute zero. Once chilled, the atoms achieve a quantum state that is easily perturbed by an outside force - and another laser beam can then be used to track them.”

It’s still early days in the development, but the team hopes to trial a prototype on land in late 2015, with miniaturisation for other applications, including cars and smart phones, to follow once the first generation is more thoroughly understood.

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