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 24^th 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

 More on:  SNAS, WAAS, GLONAS, EGNOS, MSAS.

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