Define Global Positioning System
GPS, or Global Positioning System, is a mechanism for finding out where you are on the Earth's surface. Three segments make up GPS: Satellites (space); control; and users--GPS units, or GPS receivers, and the antennas and controllers that calculate your position.
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Space
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Constellation is a collective term for a set of satellites. The GPS constellation currently has 32 satellites in orbit around the Earth.
Control
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Information from the satellite is collected by several base stations, the master station being in Colorodo Springs, Col. These stations track the status of the satellites and send them updated information such as orbit adjustments.
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Users
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Satellites send out an almanac (summary of their position) approximately every two minutes. Once the GPS unit receives signals from at least four satellites, it can calculate its position relative to the satellites. Position is given in latitude, longitude and altitude.
Uses
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GPS units are used in navigation, surveying, games like geocaching, mapping, and can be used to mark waypoints of places you want to find again.
Limitations
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GPS units are adversely affected by overcast weather, trees and tall buildings that block the signal.
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References
Resources
- Photo Credit ecran de gps image by cris13 from Fotolia.com
