Magellan Roadmate, Meridian & SportTrak GPS
GPS (Global Positioning System)
GPS is the U.S. Global Navigation Satellite
System (GNSS). A network of 24 satellites continuously transmits high-frequency
radio signals, containing time and distance data that can be picked up by any
GPS receiver, allowing the user to pinpoint their position anywhere on Earth.
Originally designated NAVSTAR (NAVigation System
with Timing And Ranging), development of GPS began in 1973. In 1978, the U.S.
Department of Defense launched the first GPS satellite, imposing SA (Selective
Availability); the intentional degradation of GPS signals to prevent military
adversaries from using the highly accurate positioning data. SA limited GPS to
100-meter accuracy for non-U.S. military users. Magellan® introduced
the first handheld receiver in 1989, making GPS available and practical for many
new industrial and recreational applications. The network required to
efficiently cover the Earth was completed with the launch of the 24th
satellite in 1994. Replacement satellites continue to be launched, each having a
life span of about 10 years.
In 2000, Selective Availability was turned off by
presidential order, giving all GPS receivers the potential accuracy of 15 meters
without the use of signal correction. The signals are available 24 hours a day
in any weather condition, everywhere around the world. When used with WAAS or
EGNOS receivers, GPS accuracy can be improved to 3 meters.