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GPS Devices - FootnotesAdvances in modern technology have resulted in affordable pocket-sized GPS devices, paving the way for failsafe route planning. Suitable for use in urban environments as well as off the beaten track, a GPS will make every journey straightforward and painless.
What is GPS ?
The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the US department of defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather condition, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS. The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours.
How does GPS work ?
The GPS satellites that circle the earth twice a day in a very precise orbit transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location. A GPS signal must be locked on to the signal of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, trackm trip distance, distance to destination, sunrise and sunset time.
How accurate is GPS ?
Today's GPS receivers are extremely accurate, thanks to their parallel multi-channel design. GPS's with 12 parallel channel receivers are quick to lock onto satellites when first turned on and they maintain strong locks, even in dense foliage or urban settings with tall buildings. Certain atmospheric factors and other sources of error can affect the accuracy of GPS receivers. GPS receivers are accurate to within 15 meters on average.
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