Galileo, Europe\'s rival to the US Global Positioning System (GPS), passed a milestone Tuesday when it pinpointed its first-ever ground location, the European Space Agency said. The spot -- ESA\'s research and technology centre in Noordwijk in the Netherlands -- was determined with an accuracy of between 10 and 15 metres (32 to 49 feet), using four satellites already in orbit. \"This is the first time ever that Europe has been able to determine a position on the ground using only its own independent navigation system,\" Galileo project manager Javier Benedicto said. \"This fundamental step confirms the Galileo system works as planned,\" added an ESA statement. A minimum of four satellites are required to fix a position in three dimensions -- longitude, latitude and altitude. The first two Galileo satellites were launched in October 2011, and two more last year. The system\'s accuracy will improve as more infrastructure is added, said the agency. ESA is set to launch four more Galileo satellites this year, contributing to an ultimate constellation of 27 orbiters and three spares. Early navigation services should be available from the end of next year.