The Global Positioning System (GPS) is a navigation system based on satellites. The GPS network operates on 24 satellites orbiting the earth. This system was initially developed by the US Department of Defense for military purposes. However the system was extended in the 1980s for civilian use. GPS works in all weather conditions and all over the world. GPS does not have any subscription fee of set up charges.
How GPS Works
GPS works through the signals the satellites transmit to earth. In other words, GPS receivers take in this information to calculate the user?s position by the method of triangulation. The GPS receiver needs signals from at least three satellites for this.
How Accurate is it?
The new generation of GPS receivers is very accurate on account of their multi-channel design. For instance Garmin has twelve parallel channel receivers that maintain strong links with the satellite network even among tall buildings or dense foliage. These receivers? average accuracy levels come up to within 15 meters. Garmin also has a new range with WAAS (Wide Area Augmentation System) that can have an accuracy of within three meters. Differential GPS is another way of achieving better accuracy of up to five meters. Here a network of towers receive GPS signals and send back a rectified signal using beacon transmitters. However this system requires that the user has a differential beacon receiver and antenna along with the GPS equipment.
The 24 satellites of the GPS network are at an altitude of 12,000 miles from the earth?s surface. They make two complete orbits around the earth in a day, traveling at about 7,000 miles an hour. These satellites are running on solar energy, with onboard back up batteries for times such as solar eclipse. They also have small rocket boosters fitted to them to keep them on the right track. Each satellite lasts for ten years and replacements are launched into the orbit as and when required.