Wednesday, June 18, 2008

Plan B - Jamming GPS

Interesting to see the analogue transmission systems attempting to bounce back using the threat of security as a main argument. The following is adapted from BBC News

Satellite navigation is used by millions of drivers as well as emergency services
The UK government is being urged to invest in a longwave radio system developed during the Second World War, as a back-up to GPS satellite navigation. Loran is less vulnerable to jamming than GPS and could protect vital infrastructure after a terror attack, a committee of MPs was told.

Doug Umbers, whose firm, VT Communications an updated version of Loran for UK coastguards said it was far more robust than GPS. Asked about keeping communications going in the event of a terrorist incident or other emergency, Mr Umbers said: "The last man standing, typically, will be the high frequency radio communications that we run, on behalf of the military."

But he said the low frequency Loran, which stands for Long Range Navigation, could be used as a back-up to GPS. "GPS is very easily jammable," he told the MPs, adding that a "biro" sized device could "stop ships in a port being able to receive GPS". But, he added, "you need a huge field of transmitters" to jam Loran. It was "highly resilient and mission critical clearly, for the maritime market, and could also have uses elsewhere".

Loran was originally developed during the Second World War as a maritime navigation aid and is based on the principle of the time difference between signals from a pair of radio transmitters. It can penetrate under water, so subs don't have to resurface to hear the message. But the rate of data transfer is slow.

Critics, who have called it for it to be switched off, say it is not cost-effective as a navigation tool and has too few users. But after nearly dying out a few years ago it is enjoying renewed interest as a possible back-up system to GPS and Galileo, the proposed European satellite guidance system.

VT Communications, last year landed a 15 year contract to develop enhanced Loran, known as e-Loran, for the General Lighthouse Authorities (GLA) in the UK, at its station in Cumbria. Hand-held GPS jamming devices, aimed at drivers worried their cars have been fitted with tracking devices, are available to buy over the internet. But security experts are also concerned about the possibility of more large scale jamming of GPS.

The US Department of Homeland Security in February this year announced it was developing a version of e-Loran to protect critical infrastructure that depends on GPS for position, navigation and timing. The UK Ministry of Defence last year carried out a series of GPS jamming trials to find out how interference could affect military personnel.

In one test it jammed GPS over a 50 square mile area of Cornwall over two days, warning emergency services and coastguards in advance. In a statement issued at the time, it said: "Although GPS provides highly accurate information, the radio signals from the satellite are extremely weak and are susceptible to both jamming and unintentional radio interference. "The trials are taking place to better understand these effects on military equipment and therefore will help to protect our forces."
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