GPS, or Global Positioning System, is a Global Navigation Satellite System that was developed by the United States Department of Defense. The GPS system is the only fully functional global navigation satellite system in the world. 

This system uses a constellation of between 24 and 32 Medium Earth Orbit Satellites. These satellites transmit precise microwave signals. These signals are picked up by GPS receivers which then can determine the current location, time, and velocity.

The official name is NAVSTAR-GPS. NAVSTAR-GPS is not an acronym but some backronyms have been created for it. The GPS satellite constellation is operated and managed by the United States Air Force 50th Space Wing.

GPS is frequently used by civilians as a navigation system. Cars frequently come with navigation systems and even cell phones have the feature. Portable GPS systems have been developed for use with everything from boats to bicycles.

The system became available to civilians everywhere after a Korean Air Lines flight was shot down into the USSR's prohibited airspace. President Ronald Reagan issued a directive making GPS freely available for civilian use as a common good. Since 1983, GPS has become widely used to aid in navigating worldwide. It is a useful tool for map-making, land surveying, commerce, scientific uses, and a number of hobbies.

A number of hobbies utilize GPS to make them safer or more fun. Mountain biking is one of many sports that benefits from the use of GPS. With the system, more areas of mountains or trails are accessible. In addition, it makes it easier to follow a trail or even to find one. In addition, should an emergency occur, it is easier for cyclists to determine their location for rescue crews.

GPS is also beneficial for cyclists who want to track their mileage and determine exactly how far they've gone. 

GPS is also good for individuals who deliver packages and documents via bicycles within a city. While these individuals may know many streets and locations, they might not know every street address. A GPS system may help a bicycle messenger deliver their assignments in more timely and efficient ways.

Prior to the GPS system, there were a number of other navigation systems developed by the Department of Defense. These systems were designed to allow ships and planes to navigate and to make it easier to stay out of trouble. Using a satellite-based system allowed for much more precision.

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Joseph Devine

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