Introduction GPS means Global Positioning System. GPS was developed by the Defense department of US. GPS was initially used by all Military forces for providing all-weather, round-the-clock navigation capabilities. Later it was opened soon to everyone else. Surveying and mapping to global change research and International air traffic management comes under the applications of GPS. How GPS works 
People often treat a GPS receiver as Global Positioning System. The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). Each of satellites are 3,000- to 4,000-pound solar-powered satellites which circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites “visible” in the sky. A GPS receiver will find out its own location by locating four or more satellites and figuring out the distance to each. This calculation is based on mathematical principle called trilateration. GPS receiver’s position is calculated on earth based on the information received from other four located satellites. This system is not 100% accurate because this method assumes the radio signals which will make their way through the atmosphere at a consistent speed and Earth’s atmosphere will slow down the electromagnetic energy down particularly as it goes through the ionosphere and trocosphere. The delay varies depending on the location where you are on Earth. So it can’t be accurate. Inorder to rectify this problem differential GPS arises. Differential GPS
The basic idea is to gauge GPS inaccuracy at a stationary receiver station with a known location. Since the DGPS hardware at the station already knows its own position, it can easily calculate its receiver’s inaccuracy. The station then broadcasts a radio signal to all DGPS-equipped receivers in the area, providing signal correction information for that area. In general, access to this correction information makes DGPS receivers much more accurate than ordinary receivers. GPS Applications GPS has a wide range of applications which fall under basic five categories 1. Location 2. Navigation 3. Tracking 4. Mapping 5. Timing
 Garmin 880 Bluetooth Automotive GPS System w/ MSN Direct & Voice Recognition |
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