A constellation of 24 GPS satellites (21 operational and 3 spares)orbits about 12,000 miles
above the Earth. The satellites zoom through the heavens at around 7,000 miles per hour.
It takes about 12 hours for a satellite to completely orbit the earth, passing over the exact
same spot approximately every 24 hours. The satellites are positioned where a GPS receiver
can receive signals from at least six of the satellites at any time, at any location on Earth— that is, if nothing obstructs the signals.
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Global Position Satellites |
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Satellite Technology:Navigation |
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Satellites in Orbit |
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Modern Navigation |
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In this section, you will gain a basic understanding of the Global Positioning System, or GPS.
GPS receivers use a special radio receiver that measures the distance from your location to
satellites that orbit the earth broadcasting radio signals.
GPS needs three components in order to work:
Satellites- Transmit radio signals to Earth
Ground Stations- Precisely control the satellites positions and monitor their status
GPS Receivers- Receives the satellites positions and how far away they are from the receiver
Satellites <---CLICK To Go To GPS Satellite Page
The solar-powered GPS satellites have a limited lifespan (around ten years). When they start to fail,
spares are activated, or new satellites are sent into orbit to replace the old ones. This gives the
government a chance to upgrade the GPS system by putting hardware with new features into space.
In GPS jargon, a satellite is the space segment.
Ground stations
Ground Stations are the control segment of GPS. Five unmanned ground stations around the
Earth monitor the satellites. Information from the stations is sent to a master control station.
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The Consolidated Space Operations Center (CSOC) at Schriever Air Force Base in Colorado is where the data is processed to determine each satellite’s ephemeris and timing errors. |
Receivers <---CLICK To Go To GPS Satellite Page
The last part of the GPS system is a receiver. A receiver is just like the radio in our car except that it receives GPS satellite signals instead of music. Anyone who has a GPS receiver can receiver the satellite signals to determine where he or she is located.
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A number of different types of GPS receivers are available, including precision surveying receivers, car navigation systems, restricted-use government and military models. And hand held consumer models designed for outdoor recreational use. Lots of GPS receiver models are on the market, and they all vary, depending on the features they have.
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Multiple Satellites |
| The reason why so many satellites are in orbit is to provide GPS coverage all over the world. Also, a GPS receiver needs information from several satellites to tell you where you’re located. |