GPS satellites transmit at least 2 low-power radio signals. Once your position has been determined, the GPS unit can calculate other information, such as: Generally, a GPS receiver will track 8 or more satellites, but that depends on the time of day and where you are on the earth. With 4 or more satellites in view, the receiver can determine your 3-D position (latitude, longitude and altitude). To calculate your 2-D position (latitude and longitude) and track movement, a GPS receiver must be locked on to the signal of at least 3 satellites. With distance measurements from a few more satellites, the receiver can determine a user's position and display it.
Essentially, the GPS receiver measures the distance to each satellite by the amount of time it takes to receive a transmitted signal. GPS receivers use this information and trilateration to calculate a user's exact location. Each satellite transmits a unique signal and orbital parameters that allow GPS devices to decode and compute the precise location of the satellite. GPS satellites circle the Earth twice a day in a precise orbit.
GPS works in any weather conditions, anywhere in the world, 24 hours a day, with no subscription fees or setup charges. The Global Positioning System (GPS) is a satellite-based navigation system made up of at least 24 satellites.
