A Global Navigation Satellite System (GNSS) is a network of satellites that transmits high-frequency radio signals containing time and distance data that can be picked up by a receiver, allowing the user to pinpoint their precise location anywhere around the globe.

There are two Global Navigation Satellite Systems currently in operation; the U.S. Global Positioning System (GPS) and the Russian GLObal NAvigation Satellite System (GLONASS). These systems are constantly being upgraded to meet higher standards of reliability. A third GNSS named GALILEO, after the Italian astronomer of the early 1600s, is currently being developed in Europe to specifically provide a higher standard of integrity and reliability, required to ensure the safety of lives during transport by air, land and sea without the use of additional augmentation systems.

While the GPS and GLONASS satellite networks are being developed to achieve maximum performance, Satellite-Based Augmentation Systems (SBAS) have been established to provide improved accuracy. SBAS provides differential signal corrections for GPS and GLONASS transmissions with the use of ground stations and geostationary satellites in specific regions. This is GNSS-1, the first phase in establishing the required integrity for high-precision satellite navigation.

GNSS-2 requires the launching of new satellites into orbit and a complete upgrade of the existing satellite systems. This second phase is already well underway. GALILEO, scheduled to begin service in 2008, is being developed to meet the standards of GNSS-2 for rapid and reliable certified precision positioning.