The United States and the European Union have agreed on how the EU鈥檚 new satellite navigation system Galileo will provide its signal. Political representatives from both sides will sign the first formal agreement at the EU-US summit in Ireland on Saturday.
The two sides have also agreed to mesh Galileo with the US鈥檚 Global Positioning System (GPS), providing a seamless network of almost 60 satellites that will improve the accuracy of both systems.
The agreement ends a five-year transatlantic dispute, which began when the EU announced plans to build a rival to the US鈥檚 GPS network. The EU is keen to have a global navigation satellite system that is independent of GPS, which is run by the US military. The EU believes this would greatly stimulate the civilian use of satellite navigation.
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But a dispute arose because the US feared that the signal modulation originally proposed for Galileo would interfere with its military operations. This was because the proposed signal partly overlapped an encrypted GPS military signal planned for 2005, known as M-code. The US also claimed that the similarity would impede the its ability to jam all signals except M-code during armed conflicts, for example.
Now the two sides have agreed that the fleet of 30 Galileo satellites, intended to be fully implemented by 2008, will use the signal modulation known as Binary Offset Carrier (BOC) 1,1. The US has also agreed to adopt this signal in its next generation GPS, which consists of about 28 satellites.
Greater precision
BOC 1,1 was recommended by the US but initially resisted by the EU. It preferred BOC 1.5, 1.5, because it would have provided greater precision. Mike Healy of EADS Astrium, the European company contracted to build prototype Galileo satellites says: 鈥淚n the end Europe moved. It wasn鈥檛 the absolute optimum solution that Europe wanted, but it was close enough.鈥�
Rene Oosterlinck, head of the Navigation Department at the European Space Agency, describes the EU鈥檚 decision to co-operate with the US as 鈥減olitical鈥�. But he says the loss of accuracy that comes from using BOC 1.5,1.5 is 鈥渋nsignificant鈥�, as both will provide vastly superior accuracy to GPS.
There is also a substantial benefit to be gained from making the two networks interoperable, he says. 鈥淲e were not obliged to co-operate with the US, but for both markets it is good to have a system that is truly compatible.鈥�
Richard Langley, a satellite communications expert at the University of New Brunswick in Canada, agrees: 鈥淚t鈥檚 basically a win-win for both sides. The benefit of having the dual constellation is a lot more significant that the marginal difference between BOC 1,1 and BOC 1.5, 1.5.鈥�
A dual system helps to increase accuracy because it doubles the likelihood of a device on the ground being within range of enough satellites to pinpoint its location.
Oosterlinck says this improvement in precision will lead to a greater demand for positioning systems. For example, GPS currently fails to pinpoint devices in built-up areas, but with twice as many satellites, its use in cars and for other location-based applications, would be far more common, he says.