The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. 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 conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.
The GPS is made up of three parts: satellites orbiting the Earth; control and monitoring stations on Earth; and the GPS receivers owned by users. GPS satellites broadcast signals from space that are picked up and identified by GPS receivers. Each GPS receiver then provides three-dimensional location (latitude, longitude, and altitude) plus the time. Individuals may purchase GPS handsets that are readily available through commercial retailers. Equipped with these GPS receivers, users can accurately locate where they are and easily navigate to where they want to go, whether walking, driving, flying, or boating. GPS has become a mainstay of transportation systems worldwide, providing navigation for aviation, ground, and maritime operations. Disaster relief and emergency services depend upon GPS for location and timing capabilities in their life-saving missions. Everyday activities such as banking, mobile phone operations, and even the control of power grids, are facilitated by the accurate timing provided by GPS. Farmers, surveyors, geologists and countless others perform their work more efficiently, safely, economically, and accurately using the free and open GPS signals.
Figure: The GPS Satellite
Why use the GPS (Global Positioning System)?
The Global Positioning System helps us to find out exactly where we are on the surface of the globe. It gives our position in latitude, longitude and altitude (height above sea level). GPS data is crucial to the GLOBE Programme. When you enter data, others might ask, “Where did they record that information?” You need to know your precise location when you collect data so that GLOBE will be able to present your information on maps. The GPS unit uses information from a series of satellites orbiting 20,200km above Earth. There are 24 satellites each sending out very accurate time signals accurate to one second in 150,000 years. That the receiver uses to work out your position. The receiver picks up time signals from at least four satellites to determine your latitude, longitude and elevation.
The Future of GPS :
Figure: Stand-Alone GPS Notional Horizontal Performance with New Signals The United States is committed to an extensive modernization program, including the implementation of a second and a third civil signal on GPS satellites. The second civil signal will improve the accuracy of the civilian service and supports some safety-of-life applications. The third signal will further enhance civilian capability and is primarily designed for safety-of-life applications, such as aviation. The figure on the right depicts the improvement of the quality of service with the additional civilian signals.
GPS Services :
GPS satellites provide service to civilian and military users. The civilian service is freely available to all users on a continuous, worldwide basis. The military service is available to U.S. and allied armed forces as well as approved Government agencies. A variety of GPS augmentation systems and techniques are available to enhance system performance to meet specific user requirements. These improve signal availability, accuracy, and integrity, allowing even better performance than is possible using the basic GPS civilian service. The outstanding performance of GPS over many years has earned the confidence of millions of civil users worldwide. It has proven its dependability in the past and promises to be of benefit to users, throughout the world, far into the future.
How It Works:
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