Magellan Maestro 4000 Instructions For Operating Manual page 24

Global satellite navigation is an exciting technology, providing enhanced
productivity and accuracy in a vast number of industries. It adds a new level
of enjoyment and safety to a wide range of navigation, sports, and
recreational activities.
A Global Navigation Satellite System (GNSS) is a network of satellites that
transmit high-frequency radio signals containing time and distance data that
can be picked up by a receiver, allowing users to pinpoint their precise
locations anywhere around the globe.
There are two Global Navigation Satellite Systems 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 being developed in Europe
specifically to 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.
2.2 How Satellite Navigation Works
Global navigation satellites continuously transmit time and distance
information as they orbit Earth in a precise formation. Navigation satellite
receivers use this information to calculate an exact location through
triangulation. Every point on Earth is identified by two sets of numbers
called coordinates. These coordinates represent the exact point where a
horizontal line, known as latitude, crosses a vertical line, known as
longitude. The receiver locks on to at least three satellites and uses the
information received to determine the coordinates of the receiving device.