What Does GPS Stand For?by Starr Kang
The global positioning system, better known as GPS, allows you to map your location, assists you with navigation, locates nearby services and shops and determines the optimal routes to take to avoid traffic congestion. However, it wasn’t until fairly recently that GPS devices became widely used, and the history and science behind these fairly ubiquitous devices still remains a mystery to many individuals.
The global positioning system was created by the U.S. Department of Defense, and the organization still operates and maintains it. The Positioning, Navigation and Timing Executive Committee manages the system; the U.S. Coast Guard oversees its civilian uses and the Air Force manages the functionality of the satellite components. GPS systems have the ability to pinpoint the precise location of an object or person within millimeters, provided the correct receiver and signaling process technology are used.
Although GPS devices are currently a standard feature in many electronic devices, they haven't always been available to the public. These devices trace their origins to earlier radio wave technologies, such as the LORAN system, which was created during World War II. The current inception of these devices began during the cold war, when GPS was used to locate enemy submarines and determine the best position for ground troops. The introduction of the GPS system eliminated the need for thousands of disparate navigational aids. A large part of the success of the system is that it can be accessed though fairly inexpensive devices, such as GPS navigational systems in vehicles and cell phones.
Components of the GPS Network
The GPS system relies on a network of satellites and ground stations located at various Air Force bases. At least 24 satellites navigate the earth at any given time, at a distance of about 11,000 miles. In 2011, the system expended to incorporate 27 satellites for better coverage, and the system is currently known as "expandable 24." These satellites are positioned alone six orbital planes, a configuration that allows four satellites to be viewed from any given location on earth. Although the Air Force runs up to 31 satellites at a time, the 24-satellite configuration is still the core of the system. Ground control stations are also necessary to ensure accurate positioning data. The Master Control ground station is housed at Schriever Air Force Base in Colorado, and other ground stations are located in such places as Hawaii, Ascension Island, Diego Garcia and Kwajalein Atoll.
How It Works
The satellite network relies on radio transmissions. Satellites simultaneously broadcast their location and the current time. These signals travel at the speed of light in a vacuum, but still arrive at different times to GPS receivers, because of the differing locations of the satellites sending the transmissions. This time differential allows the GPS receivers to determine the precise location of the satellite sending the data. When GPS receivers obtain data from at least four satellites, they can pinpoint the location of an object. Originally, the DoD placed errors in the timing of transmissions to prevent civilian receivers from obtaining data that provided a location more precise than 100 meters. That restriction was lifted in 2000, but there are still different GPS systems, a Precise Positioning Service for authorized military personnel and a Standard Positioning Service for civilian use.
Many different manufacturers sell GPS devices, which can be purchased at electronics stores or online. Some of the most commonly known GPS providers include Garmin, TomTom and Magellan. Additionally, GPS service also is available on many smartphones. Some GPS devices require a service fee or update fee, while others provide service and updates as part of the initial purchase cost.
When purchasing a GPS device, consider the features you need, such as the size of the screen and the frequency of the updates. You should also consider how you’ll mount the device in your vehicle, and you may need to buy a separate kit to install the device. If you frequently travel and need precise directions and regular updates, you’ll likely spend more than if you occasionally use a GPS device to navigate around town.
- link GPS.gov: Space Segment and Satellite Orbits
- link Federal Aviation Administration: Navigation Programs - Global Positioning System
- link Smithsonian Institute: How Does GPS work?
- link U.S. Navy: Navstar GPS Operations: USNO Navstar Global Positioning System
- link University of Washington: Fundamentals of the Global Positioning System
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