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Global fix
04 May 2002
From New Scientist Print Edition.
Gerry Byrne
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Its power is beguiling. It can tell you your exact location, any time, anywhere. It can guide anything from cruise missiles to cruise ships, jet fighters to airliners. It's become a vital tool for power companies and phone networks. And now it promises to direct your car around traffic hold-ups, tell the emergency services where you are, and open up a new world of commercial opportunity by beaming restaurant menus, entertainments listings or adverts for local services direct to your mobile phone.
That, at any rate, is the aim of the Global Positioning System, a network of 24 satellites girdling the Earth. Operated and controlled by the US Department of Defense, GPS signals are available free for anyone to use around the world. But the reality doesn't always quite live up to expectations, and now the European Union is planning to spend a small fortune launching a system of its own, called Galileo. On the face of it, Galileo will do pretty much the same as GPS, so what's the point? Is Galileo an expensive piece of European flag waving, or will it, as its backers claim, transform location-based services available worldwide?
The first GPS satellite was launched in 1978 to give American soldiers, ships and planes the advantage in battle by providing precise navigation information in all weathers, day or night (see "Sky wars"). These satellites also beam out a signal that can be picked up by civilians. These days, a hand- held GPS receiver costing just over £100 will tell you your position to within 20 metres, and the business world has been quick to pick up on the potential of GPS. Already, ships, airliners and hill walkers use GPS to pinpoint their position. Car rental and insurance companies use it to track vehicles. And thanks to GPS, pilots of small aircraft will soon be able to land at any small American airstrip in any weather—a facility previously available only to airlines operating at major airports. Even farmers are starting to benefit: tests of GPS-equipped tractors show they will be able to plough more precisely, with no one in the driving seat.
But in future, the biggest market for GPS receivers is expected to lie elsewhere, with enticing consumer applications such in-car navigation, and unashamedly commercial location-based services such as directories and details of local restaurants for mobile phones. By 2003, it's predicted, these two sectors will together be worth some $8 billion a year, or about half the total market for GPS-based products and services.
Laws are being wheeled out on both sides of the Atlantic to make the most of satellite navigation technology. In the US, for example, legislation known as the E911 mandate requires that in future all mobile phones must be fitted with a system to help the emergency services locate a caller. Dial 911 to summon help and your mobile phone will become a distress beacon, broadcasting its position to the nearest firefighter or police patrol. Cell-id, the technology available with today's mobile phones, can only pin down a phone to within an area of 10 square kilometres or so (New Scientist, 21 October 2000, p 44). But under E911 all 911 calls should eventually be located to within 50 metres.
One of the cheapest and most obvious ways to implement this is to build a GPS chip directly into the handset, and almost three-quarters of mobile phones are expected to include such a chip by 2006.
The EU plans to implement similar legislation, the E112 mandate, in the next few years. So far, however, most large-scale GPS applications planned for Europe focus on government-driven public transport projects or "intelligent vehicle highway systems". Some European cities such as Genoa and Helsinki already use GPS to monitor the position of buses, trams and trains, to optimise efficiency and help passengers find the quickest way across town. And in Britain, for example, the government is examining proposals from the Commission for Integrated Transport to reduce congestion by equipping vehicles with satellite navigation devices that will be used to charge drivers who use toll roads or drive into busy city centres. It has also commissioned a trial to test GPS-controlled devices that will slow cars to whatever speed limit applies on their section of road.
What attracts governments and business most about GPS is that, in principle at least, it helps get this kind of large-scale transport project up and running without the need to build a costly infrastructure of cameras, or the transmitters and receivers required by a more accurate version of the cell-id system. The American satellite network is already in place. All that's needed to complete the picture is a small, cheap transceiver chip built into each vehicle.
Yet these grand plans don't quite tie in with the practical realities of GPS. It is, remember, a military system. Hanging over everything like the sword of Damocles is the fear that during a security alert, the US will put the needs of the military first, and perhaps reduce the accuracy of the GPS signal or even switch it off altogether, if that suits its purpose. And as Europe becomes more and more dependent on GPS services, being reliant on the goodwill of the US could put it increasingly at a diplomatic disadvantage.
Besides, says Walter Blanchard, ex-president of the Royal Institute of Navigation, how can European legislators pass laws requiring the use of GPS devices to charge for road use, say, if those countries have no input into the management of GPS. "Would it be possible to legislate for its use?" he asks.
There are more mundane, practical problems, too. The GPS signal broadcast by the satellites is weak: by the time it reaches the receiver the signal is just a few microwatts, way below the level of many radio transmissions. This makes GPS signals vulnerable to interference, by accident or intention.
The extent of the problem was revealed last September, in a study prepared by the US government's Volpe National Transportation Systems Center. The study assessed the vulnerability of GPS to every major type of interference, and was released at a crucial time for transportation policy in the US. The US Coast Guard, along with the Federal Aviation Administration, had been preparing for the phase-out of the nation's networks of conventional radio navigation beacons in favour of cheaper systems based solely on GPS. A similar pattern is being followed in many countries, and in many different applications, around the world.
But that, warns the Volpe report, is folly. It found that GPS is prone to solar, atmospheric and electronic interference and can't always be relied upon. Assuming the signal is always present and correct will lead to trouble, it suggests. To make the point, the report cites the case of the cruise liner Royal Majesty, which ran aground in June 1995 on a sandbank off Nantucket island, Massachusetts. The crew had faithfully followed the course indicated by their GPS navigation system, unaware that the satellite navigation antenna had been disconnected.
And although there have been no confirmed incidents of large-scale jamming, there have been many reports of the sudden and inexplicable loss of the signal aboard aircraft, including a Continental Airlines jet above New York and a British Airways flight over central France. In another incident, all GPS navigation signals disappeared for 18 minutes over Oklahoma, Kansas and Nebraska when the satellites malfunctioned.
GPS users in urban areas face even more persistent, if less dramatic, problems. Bridges, buildings or even the leaves on trees can block out GPS signals or create confusing reflections. The result, according to one EU estimate, is that only 55 per cent of built-up areas have useful GPS coverage. Things get even worse if you are on the move. Satellite navigation works best when at least three satellites, and preferably four, are in direct line of sight from the receiver. The longer you are prepared to wait for new satellites to come into view, the more accurate your fix will be. But if you are constantly changing your position—driving through narrow city streets, for example—then any fix you get is likely to be rough.
Washington Ochieng from the Centre for Transport Studies at Imperial College, London, demonstrated this in a series of tests around the city last year. He used various GPS receivers fitted to a car and cross-checked the results with the car's actual location. During some two hours of tests using a GPS unit which offers centimetre accuracy in open spaces, he found that accuracy to 5 metres or better was available only 17 per cent of the time. Even with a GPS receiver optimised for use on the move, he found that most fixes were accurate down to only 30 metres, which is not good enough for many real-world applications.
Although it is possible to improve on this performance, this can be costly and isn't always terribly effective. For example, manufacturers can add dead reckoning or inertial navigation systems to an in-car GPS unit, which in theory will update a vehicle's position even when the GPS signal has faded. But without constant updates from GPS, their calculations quickly start to drift. Clearly, accuracy and urban mobility do not yet go hand in hand—especially in Europe where roads are narrower and cities more densely built-up than in the US.
So how will this picture change in 2008, when the Galileo satellite network is planned to be up and running? Clearly, one benefit to European nations is that they will have control over their own satellite navigation system. Member states will at last be able to develop their own strategies for using the signals, without fear that they might be switched off or degraded without warning (New Scientist, 30 March, p 5). And because Galileo has been designed to work in parallel with the existing American system, reception should become more reliable—there will be almost 60 satellites to lock on to rather than just 24. According to a report from the EU Directorate General for Energy and Transport, using both systems together will boost urban coverage to 95 per cent, as well as improving accuracy overall. And with two separate systems to rely on, satellite navigation should be less vulnerable to interference or jamming.
In the US, the Volpe report largely welcomes Galileo for the improvement it will bring to the accuracy of satellite navigation as a whole. But the government's attitude is less wholehearted. The latest Federal Radionavigation Plan makes no mention of it, and a letter sent to European defence ministers by the US Deputy Secretary of Defense Paul Wolfowitz argues that Galileo is unnecessary. He insists that GPS already provides an excellent worldwide service, and claims that the frequencies Galileo plans to use are so close to those earmarked for future GPS upgrades that they could cause major headaches for users because of interference. EU officials point out that the two sides are negotiating over this issue, and that any problems should be easy to overcome.
But many observers dismiss Washington's professed concern for civilian users of satellite navigation systems as nothing but a smokescreen. "Most American users of satellite navigation are in favour of Galileo," says Keith McDonald, formerly scientific adviser to the US Department of Defense and one of the architects of GPS. The real aim, he argues, is to maintain military superiority. The Pentagon's worry is that its enemies could use the system to direct weapons against American targets. And if Galileo's operating frequencies are close to those used by the US military, blocking Galileo's signal may also impede their own. "The US Department of Defense wants Galileo stopped because it will be very expensive to jam in time of military conflict," says McDonald.
The US also has economic reasons for fearing a competitor to GPS. The industry that designs and manufactures GPS devices brings in $8.5 billion in the US alone. Europe wants to grab a chunk of this market, and expects Galileo to provide the spur for the growth of a similar industry of its own.
Undaunted by Wolfowitz's letter, European transport ministers have approved funding that puts the first of the Galileo constellation on track for a 2006 launch. But the debate on how Galileo will earn its keep has hardly begun. Galileo will offer a free signal that's more powerful and accurate than is currently available from GPS. However, to generate revenue, users who need the highest precision have to pay for a separate signal that allows them to evaluate Galileo's integrity. This will constantly monitor the health of each satellite in Galileo's constellation and warn subscribers if any signals have become degraded.
A study last year by British consultancy PricewaterhouseCoopers found a strong demand for such a signal, but some experts doubt that this will yield significant income.
David Broughton, director of the Royal Institute of Navigation, is one of them. He suggests instead raising income from a levy on sales of receiving equipment. He points out that the EU is already backing EGNOS, an augmented GPS system based on a network of geostationary satellites which will perform a similar task and will, the EU has promised, be provided free of charge. "Users might ask why they should pay for Galileo when they are getting a similar service free from EGNOS," says Broughton.
And Galileo's profitability could also suffer if its launch schedule slips. America plans to launch new satellites that will improve GPS coverage. But most aren't scheduled to come on stream until after Galileo is operating, allowing the European project a vital head start. Any delay, however, and the American system will regain the edge.
There are technical issues, too. Receivers should be able to pick up signals from both Galileo and GPS, so mobile urban coverage should improve. But the gains may be less than dramatic, Ochieng warns. "If you've been getting 90 per cent coverage for a mobile application, expect to see it go to maybe 92 per cent with Galileo," he says.
And now there's one more threat looming that could undermine the future of both GPS and Galileo: a new generation of wireless local area networks that are predicted to outperform existing standards such as Bluetooth or 802.11x. These new networks broadcast a weak but ultrawide spectrum of radio frequencies—known as spread spectrum—that overlap with those allotted to GPS and Galileo. According to a report by the US National Telecommunications and Information Administration, airline and Department of Transportation officials are seriously concerned about the possibility of ultra-wideband wireless signals interfering with GPS reception. Tests by the Federal Communications Commission showed that these signals can interfere with airport landing systems and satellite communications. In cities where every business and many homes could one day be using wireless networks, satellite navigation systems could be blinded. The US is still waiting on the results of tests to assess their impact on satellite navigation. In Europe the debate hasn't properly begun.
If interference does prove a problem, the regulators will have to hammer out a compromise that can protect satellite navigation without slowing the roll-out of the new networks.This won't be easy—the new wireless technology is backed by big hitters such as Intel and Sony. Get it wrong and both technologies could end up underperforming. Right now only one thing is certain: the battle for the airwaves has just begun.
Gerry Byrne is a writer based in Ireland
City of the lost
From issue 2341 of New Scientist magazine, 04 May 2002, page 32
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