Global Positioning System (GPS)

United States Department of Defense developed and operates the Global Positioning System (GPS). Originally the system was used to provide twenty – four hour navigational capabilities, for military ground, sea, and air force. The modern GPS is a satellite navigational system, supported by twenty-four satellites that orbit the Earth, and sends a signal to receivers on Earth. Satellites orbit Earth, approximately 12, 000 miles above the surface. Build within each satellite, is an atomic clock that is precise, within a billionth of a second.

A transmission is send from the satellites to Earth, at the speed of light (approximately 186,000 miles per second). The longer the signal travels to a receiver, the further away the satellite is located. Knowing this distance, through triangulation and using three satellites, then can calculate the longitude, latitude, and time, on the Earth’s surface. Also, using a fourth satellite the GPS can determine altitude. Application for Global Positioning System, include cartography, forestry, mineral exploration, and location of planes, wildlife habitation management, and monitoring the movement of people.

Global Positioning Receivers can store locations, which can be utilized to plot positions on a map or use to retrace to original starting point. Example of this application: Global Positioning Receiver installed within a car. The driver programs the unit with the address of destination, and starting address, before departing. The GPS receives the signal from the orbiting satellites, to correspond with exact directions, along the route.

Some GPS systems provide the user with an audible sound of a human voice (man or woman), providing directions along the route (“turn left or turn right”), until arriving at the destination. If the driver turns onto a wrong direction, the system would inform the driver of the mistake, and how to return back onto the original route. The Global Positioning System is accurate within one degree. All receivers have an external antenna option, which allows the receiver to placed inside a vehicle.
The signal from a Global Positioning System can be interrupted or blocked in certain locations. Tall buildings, mountains, highway overpasses, and other large objects, can interfere with the signal. Generally in a moving vehicle or boat, the signal interruption, returns within seconds.

Three Basic Kinds of Global Positioning Systems

Industrial Navigation System for surveying and data collection. Archaeologists use this type of receiver. Medium cost units intended for marine and aviation users. Handheld GPS Receivers for outdoor use. These systems are durable for hikers, hunters, and boaters. A waterproof case can be purchased to prevent any water damage. Only problem with these handheld devices, batteries need to be changed or purchase a rechargeable Twelve Volt Battery. Garmin International sells the most Global Positioning technology systems. Their products are used for flying, boating, driving, hiking and other activities. Maps can be uploaded from a personal computer.

The Federal Aviation Administration and Department of Transportation are developing Wide Area Augmentation System (WAAS), which is a system of satellites, and ground stations that enhance the GPS signal, to provide better position accuracy. Often the accuracy, integrity and availability are interrupted, by ionospheric disturbances, timing and satellite orbit errors. The WAAS will improve basic GPS accuracy to approximate seven meters vertically and horizontally. There is no additional receiving equipment and no additional cost. The system is available in North America.

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