By Han Lin

    BEIJING, April 15 (Xinhuanet) -- Global Navigation Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage.

    GNSS allows small electronic receivers to determine their location (longitude, latitude, and altitude) within a few metres using time signals transmitted along a line-of-sight by radio from satellites. Receivers on the ground with a fixed position can also be used to calculate the precise time as a reference for scientific experiments.

    China's Compass: 

    Compass, China's independent global satellite navigation system, is planned to complete by launching about 30 more orbiters before 2015, with 10 navigation satellites into the space in 2009 and 2010. The current Compass system only provides regional navigation service within China and neighboring regions.

    U.S. Global Positioning System:

    Global Positioning System is a global navigation satellite system developed by the United States Department of Defense and managed by the United States Air Force 50th Space Wing. It became fully operational in 1993. The system allows users to determine their positions within a few meters. As of 2009, GPS is the only fully operational GNSS.

    Russian Glonass:

    Glonass, a Global Navigation Satellite System, is the Russian version of the U.S. Global Positioning System and is designed for both military and civilian use. But Glonass is a GNSS in the process of being restored to full operation. Russia launched a carrier rocket to put three navigation satellites into orbit at the end of 2008, making its navigation satellites to reach 19.

    EU's Galileo:

    The Galileo project, launched in 1999, is a joint initiative of the European Commission and the European Space Agency. Under the agreement signed by the EU transport ministers in November 2007, Galileo will be put into operation by 2013.