Galileo and GPS. Where it’s at

Date: 31/01/04

A European satellite-navigation network is on its way

IT IS now almost two years since the European Union decided to go ahead with plans to launch a satellite-navigation network to rival America's existing Global Positioning System (GPS). For much of this time, Galileo, as the European system is called, met with staunch opposition from America. However, a round of talks last November seems to have assuaged American concerns. The final details remained to be negotiated in talks in Washington, DC, on January 29th and 30th, as The Economist went to press. But the outlook for an agreement was good.

The core of the disagreement between the EU and America was whether the signals from the two competing systems might interfere with one another. More specifically, the Americans wanted the ability to jam Galileo without rendering GPS signals ineffective. The agreement reached in November was the first step in this direction. In return for the modification of Galileo's signals, the Americans agreed to give Europe technical assistance in developing Galileo, and to make sure that the third generation of GPS, to be deployed in 2012 (Galileo should be operational by 2008), will conform to Galileo's standards. This will aid the interoperability of the two systems, which is a commercial goal of both sides. It will also, in principle, give the Europeans the ability to jam the American signals in the event of a crisis in which the two sides' interests differ.

There is a bewildering array of different sorts of signals involved in each network. GPS currently has two, a civilian channel known as C/A and a military one, Y-channel. Plans for an additional military channel, called M-code, are in the works. Galileo will debut with five different signals: one freely available to all, like the GPS C/A signal; a commercial service which is more precise; a “safety-of-life” service that can be used for critical applications such as automatically landing aeroplanes; a “public regulated service” (PRS), which will be used by the EU's governments, and presumably, their armed forces; and a fifth, unique, service that combines positioning information with a distress beacon, which could be used by ships at sea or intrepid mountaineers. The negotiations in November resolved a conflict between America's M-code and the European PRS. What remains is to harmonise Galileo's free signal with the M-code.

Both systems rely on signals precisely timed from atomic clocks carried by the satellites (GPS has 24 satellites, Galileo will have 30). A user looks at the time on at least four satellites, and triangulates (or, perhaps, “quadrangulates”) between them to find his position. Differences in the details of the different signals are what make the “premium” applications. Some are more precise than others, and they also have different levels of encryption, to prevent unauthorised users from accessing them.

What makes the situation bizarre is that several of these signals will overlap with one another, within a frequency range known as the L-band (this is about 10 times higher than the frequency used by commercial FM radio stations). That can be done using a technology called spread spectrum, which is now common in mobile telephones.

The trick is to embed the signal in a dense “pseudorandom” sequence (it is pseudorandom because it looks random but is actually generated by a computer program). To an uninitiated recipient, the result appears to be noise. However, if the recipient knows the right starting values for the program, he can regenerate the sequence and disentangle the original signal. The signals can overlap because each, to the others, resembles noise.

Galileo will be in part a commercial system. A concessionaire will get the right to operate the system for a fixed period in return for plunking down two-thirds of the deployment costs - around €2.2 billion ($2.8 billion). But control and ownership of the network will remain with the EU (most of whose members are, or soon will be, America's military allies in NATO), through a yet-to-be-formed, and ominously titled, “Surveillance Authority”.

This means that American fears about the use of Galileo during, say, a crisis in the Taiwan Strait, are perhaps overblown. Despite the fact that China recently agreed to pay €200m towards Galileo's development, it will not have access to the PRS channel, nor a say in how Galileo is run during a crisis, according to Paul Flament, an engineer at the European Commission who is working on Galileo. The same is true of other prospective partners such as India and Israel. (Brazil is involved in an early stage of negotiations as well.)

Sceptics question whether Galileo will indeed prove profitable. They suggest that the concessionaire might face huge liabilities in the event of an accident. But at least four consortia are bidding to become the concessionaire, and these consortia include such firms as EADS (the owners of Airbus) and Alcatel. Optimistic projections talk of 2.5 billion users by 2020. If even a small fraction of that number needed additional precision and were willing to pay for it, the business would be lucrative. America may yet regret not privatising part of GPS.

A European satellite-navigation system is on its way.

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