What is GPS – Global Positioning System
July 31st, 2007 by Annkur
The Global Positioning System (GPS) is currently the only fully functional Global Navigation Satellite System (GNSS). Utilizing a constellation of at least 24 medium Earth orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its location, speed and direction.
Developed by the United States Department of Defense, it is officially named NAVSTAR GPS. The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year,[2] including the replacement of aging satellites, and research and development. Despite this fact, GPS is free for civilian use as a public good.
GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user’s exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user’s position and display it on the unit’s electronic map.
Here are some other interesting facts about the GPS satellites
* The first GPS satellite was launched in 1978.
* A full constellation of 24 satellites was achieved in 1994.
* Each satellite is built to last about 10 years. Replacements are constantly being built and launched into orbit.
* A GPS satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended.
* Transmitter power is only 50 watts or less.
Read more at http://en.wikipedia.org/wiki/Global_Positioning_System
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Categories: Concept / Educative | Tags: Global Navigation Satellite System, Global Positioning System, GNSS, gps, NAVSTAR, satellites
