|
Role of GPS in navigation, Fleet Management and other Location Based Services
GPS Uses in Everyday Life The GPS system was developed to meet military needs of the Department of Defense, but new ways to use its capabilities are continually being found. The system has been used in aircraft and ships, but there are many other ways to benefit from GPS. Vehicle tracking is one of the fastest-growing GPS applications. GPS-equipped fleet vehicles, public transportation systems, delivery trucks, and courier services use receivers to monitor their locations at all times. GPS is also helping to save lives. Many police, fire, and emergency medical service units are using GPS receivers to determine the police car, fire truck, or ambulance nearest to an emergency, enabling the quickest possible response in life-or-death situations. Automobile manufacturers are offering moving-map displays guided by GPS receivers as an option on new vehicles. Several car companies are demonstrating GPS-equipped vehicles that give directions to drivers on display screens and through synthesized voice instructions. GPS in Navigation What is navigation? Since prehistoric times, people have been trying to figure out a reliable way to tell where they are, to help guide them to where they are going, and to get them back home again. Cavemen probably used stones, when they set out hunting for food. These marks used to erased no. of times. The earliest mariners followed the coast closely to keep from getting lost. The next major developments in the quest for the perfect method of navigation were the magnetic compass and the sextant. The needle of a compass always points north, so it is always possible to know in what direction you are going. The sextant uses adjustable mirrors to measure the exact angle of the stars, moon, and sun above the horizon. However, in the early days of its use, it was only possible to determine latitude (the location on the Earth measured north or south from the equator) from the sextant observations. Sailors were still unable to determine their longitude (the location on the Earth measured east or west). In 1761, a cabinetmaker named John Harrison developed a shipboard timepiece called a chronometer, which lost or gained only about one second a day - incredibly accurate for the time. For the next two centuries, sextants and chronometers were used in combination to provide latitude and longitude information. In the early 20th century several radio-based navigation systems were developed, which were used widely during World War II. A few ground-based radio-navigation systems are still in use today. One drawback of using radio waves generated on the ground is that you must choose between a system that is very accurate but doesn’t cover a wide area, or one that covers a wide area but is not very accurate. High-frequency radio waves (like UHF TV) can provide accurate position location but can only be picked up in a small, localized area. Lower frequency radio waves (like AM radio) can cover a larger area, but are not accurate. Scientists decided that the only way to provide coverage for the entire world was to place high-frequency radio transmitters in space. A transmitter high above the Earth sending a high-frequency radio wave with a special coded signal can cover a large area. This is one of the main principles behind the GPS system. Navigation can be required in land, air and water or in sea. Everyplace navigation can be provided with some modification in the process of getting the data and way of processing of data and accuracy of the data required for each purpose. Navigation in Land GPS improves efficiency on land as well. The capabilities of satellite navigation, when coupled with communications and modern computerized management systems can help meet many of the transportation challenges facing all modes of surface transportation. Currently, it is being used to add a new dimension for automatic vehicle location and in-vehicle navigation systems. GPS helps motorists find their way by showing their position and intended route on dashboard displays. 
The NAVSTAR and GLONASS systems use the principle of trilateration. That is, the user’s receiver determines the distance from the user to each of several satellites. Since the positions of the satellites are known, either through previous publication or as part of the satellite’s broadcast information, the user’s position can be calculated. Display of the position of the vehicle can be taken on an instrument of a size of a mobile phone or palmtop. A central monitoring station or service providing central station can observe the position. The various services that can be provided by the central monitoring station can be as follows:
|