Global Positioning System (GPS) is the most accurate and the most sophisticated navigation system in the world. The GPS receiver that enables you to determine your location is one of the three main components of the GPS system. The other two components are a constellation of 24 satellites (actually 30) and a few ground stations that constantly monitor these satellites. The GPS receiver just picks up the signals that are constantly transmitted by satellites and process them to determine its location. With the GPS system, you can know where you are even in unknown places as well as the speed and direction if you are moving.
It was US Department of Defense that started developing a navigation system based on satellites during early nineteen sixties. Given name as NAVSTAR, the GPS underwent a gradual evolutionary process during the next three decades. Many GPS satellites were launched during this period on experimental basis and finally NAVSTAR was successfully completed in 1993. Presently there are two dozens of GPS satellites that orbit the earth and assist the navigation system used by military as well as civilians. The maintenance of these satellites alone cost US government nearly 800 million every year not to mention the billions of dollars spent for building satellites and their launching.
GPS was initially used for military operations, weapon systems and tracking missiles. However, within a decade, it was made available for people in all walks of life and soon it became an essential navigation tool to be used in airplanes, ships, cars and trucks. It has also become a valuable aid to map makers, explorers, scientists, adventurers and rescuers
Today, GPS has revolutionized our personal navigation system. You no longer require any maps or compasses when you travel in unfamiliar places, because your small, easy-to-carry GPS receiver provides all traveling supporting information. GPS enabled transport vehicles are quite safer when compared with vehicles without GPS system. They will show your location, speed and direction and even give directions to reach your destination. As GPS provides coverage over the entire globe and your GPS receivers come with pre-loaded maps of any places, your navigation has never been safer before.
The parts of GPS
There are three major components that make up the GPS. They are satellites, monitor stations and GPS receivers.
Satellites
Your GPS receivers constantly decode the signals received from the satellites to determine your location. Presently, there are 24 GPS satellites that orbit the earth and transmit signals to GPS receivers. The additional 6 satellites are presently non-operational. Each satellite moves in a circular path with a radius of 12,000 kms from earth and completes two revolutions everyday. The GPS satellites are stationed on the orbits in such a way that you can get signals from at least 4 satellites from any place at any time.
The data provided by GPS satellites are of three types: almanac, ephemeris and the pseudorandom code. Almanac is nothing but a logbook that records data about the position of satellites while ephemeris provides latitude and longitude details of any place on earth. Each satellite has a unique pseudo-random code so that the GPS receiver can identify the specific satellite and process its signals. There is an atomic clock onboard in the satellite to measure the time taken by the signals to reach the earth. As atomic clock is the most accurate clock, so GPS usually provides the most accurate time with a preciseness of nano-seconds.
Monitor stations
The five ground stations which are located around the globe, constantly track the path of satellites to send and receive data from satellites. Apart from the master control station at Colorado, the other monitor stations are located in Falcon AFB, Hawaii, Ascension Island in the Atlantic, Diego Garcia in the Indian Ocean and Kwajalein Island in the South Pacific. The master control station receives the information collected by monitor stations and constantly sends updated information through the antennas to the satellites back to synchronize the atomic clock in the satellites and to correct the ephemeris of each satellite.
GPS receivers
GPS receivers are small computing devices that receive signals from GPS satellites and process them to determine a specific location.
GPS receivers are generally made up of following components:
- An antenna which can be adjusted to gather signals sent by the satellites.
- Processors to decode the signals and do complex mathematical functions
- An accurate clock often based on crystal oscillator to measure the time.
- A display screen to show location and movement details
Initially, GPS receivers had just four channels which means they could track four satellites simultaneously. However, with time and technological advancements, present GPS receivers can have 12 – 20 channels. They come with both portable and mountable designs and hundreds of models are available depending on their in-built features. The hand-held GPS receivers weigh just a few ounces and you can take them to anywhere you like to assist your navigation while the mountable GPS receivers can be installed in cars, trucks, ships, airplanes etc.
You can read expert GPS Reviews and find the latest GPS Sat Nav systems in this website.
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