The satellites will orbit at about 23,000 km

Positioning satellites transmit signals which, when picked up on the ground, allow someone to pinpoint their exact location on a map. With Galileo, you would be able to do this with accuracy down to one metre.

The system would also used to provide surveying references for building roads, bridges and cities.

In future, the satellite network should have many other applications as well, such as in new personalised services for mobile phone and pocket computer users.

Where does current information come from?

There are two satellite positioning systems already in use. One is the Global Positioning System (GPS) run by the United States.

The other is the Russian network, known as Glonass. Both have military applications and there is no guarantee of an uninterrupted service. Military interests could dictate that the services be degraded or taken offline altogether to prevent the enemy using the system.

How much will Galileo cost?

Galileo will cost 3.2bn euros (�1.9bn). About a third of this will be spent on development.

When will the satellites be launched?

Most of the satellites will be launched in 2006 and 2007. They will orbit about 23,000 kilometres above the Earth, where their positions will be monitored by a series of ground stations.

Service centres will pass on information to users, including transport authorities, companies and people with mobile phones containing special receivers.

Does Europe need Galileo?

This is a matter of much debate. There are various considerations including the cost to the taxpayer, job creation in the European hi-tech sector and security issues. Arguments for Galileo include:

• Europe needs its own system if new services relying on satellite positioning are to be developed - these would include safety-critical applications where lives would be put at risk if the service could not be guaranteed
• Galileo will achieve better coverage over Northern Europe
• Galileo will be under civilian control - military interests would not take precedence
• It will create more than 100,000 jobs.

Arguments against the project include:

• High cost to the taxpayer
• Duplication of existing systems
• Concern, particularly in the United States, that Galileo could pose a security threat
• Few benefits to the consumer.