What is GPS?

At this point, almost everyone has heard of GPS, whether in association with aircraft, cars, biking, running, and more. But what exactly is GPS, and how does it work? Why is it such a valuable tool with so many different applications? GPS, or Global Positioning System, is a navigation system that utilizes over 30 satellites located in the Earth's orbit to calculate the specific locations on the Earth's crust. Though it was first designed and used by the United States Department of Defense with only 24 satellites, in 1983 GPS was opened to civilian application due to the attack of a civilian Korean aircraft over Soviet skies. The great thing about this system is that it is available 24 hours per day, anywhere on Earth, with no charges or fees associated with it.Each GPS satellite orbits the Earth two times per day with an extremely precise path. Signal information in radio form can be transmitted to GPS receivers on the Earth's surface that interpret the information and calculate the device's exact location through triangulation. Even though the satellites are moving at great speeds (upwards of 7k miles per hour), the GPS receiver compares the time of a signal transmission to the time it was received to measure the distance between the GPS receiver and the satellite. By taking the same measurement with a few more satellites, the receiver can determine the exact position of the device. This can then be displayed on an electronic map or in latitude and longitude form. This may seem like quite a lot of work, and at one time triangulation did involve a fair amount of arithmetic, but with modern GPS devices, the transmissions and calculations can take a matter of seconds. GPS receivers need a secure signal from three or more satellites to determine the latitude and longitudinal location, and continue to track the movement of the device, but with four or more satellites a compatible receiver can provide a three dimensional location, including altitude. After calculating the position of the receiver, the speed, track, distance to destination, bearing, as well as other measurements can be established. GPS receivers have come a long way in the past twenty years. A 12 parallel channel GPS receiver can be accurate to 45 to 50 feet, even amongst tall buildings or dense tree cover. Even newer receivers using Wide Area Augmentation can be accurate to less than 10 feet. This accuracy can be obtained with direct reception from satellites, but through the implementation of Differential GPS the signals can be corrected within 10 to 15 feet. This is achieved through beacon transmitters located on towers that receive satellite signals and transmit a corrected signal to a GPS receiver. A differential beacon receiver must be used in conjunction with a GPS receiver in order to take advantage of these corrected signals. Assisted GPS, or aGPS, is another technique commonly used in most mobile phones, which provides very fast signal correction, typically less than 15 seconds. It also improves the accuracy to 3-5 meters in optimal conditions. In the next generation of aGPS technology, included in Qualcomm chipsets, 2-3 meter accuracy will be yielded, and reception will be improved in urban areas, canyons, and dense foliage conditions.Whether you are navigating through traffic, piloting an airplane, or trying to improve your running routine, GPS provides valuable and accurate information. GPS is taking our civilization to a new level of precision, from daily routines to our understanding of the world and the universe we live in. Think about ways that a GPS receiver could make your life easier or more efficient.

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