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ABSTRACT
Where am I? Where am I going? Where are you? What is the best way to get there? When will I get there? GPS technology can answer all these questions. GPS satellite can show you exact position on the earth any time, in any weather, no matter where you are! GPS technology has made an impact
On navigation and positioning needs with the use of satellites and ground stations the ability to track aircrafts, cars, cell phones, boats and even individuals has become a reality.
This paper describes the Global positioning system (GPS) satellite. It depicts what GPS satellite is, how it works and its tracking features. This paper also gives how
the GPS satellite has been used to compute position and time, gives the details of various
segments in which the GPS system is useful. The paper gives the benefits of GPS satellite such as ability to track an object, due to reduced cost it is more affordable for everyone and helps you to find out where you are and how to get to your destination,
where ever you are going on land or sea.,
Applications such as military, car alarms, home security and home monitoring
INTRODUCTION
Trying to figure out where you are and where you're going is probably one of man's oldest pastimes. Navigation and positioning are crucial to so many activities and yet the process has always been quite cumbersome. Over the years all kinds of technologies have tried to simplify the task but everyone has had some disadvantages. Finally, the U.S. Department of Defense decided that the military had to have a super precise form of worldwide positioning. And fortunately they had the kind of money ($12 billion!) it took to build something really good. The result is the Global Positioning System, a system that's changed navigation forever.
GPS initially created by the U.S Defense Department for the military has later been made available to the public. GPS technology is not just a handheld “help-me-find-my-way-home” operation anymore. GPS is finding its way into cars, boats, planes, construction equipment, moviemaking gear, farm machinery, even laptop computers. Move over Mr. Bell, it won’t be long until GPS will become as basic as the telephone.
ALL ABOUT GPS
A constellation of 24 satellites
A system of satellites, computers, and receivers that is able to determine the latitude and longitude of a receiver on Earth by calculating the time difference for signals from The Global Positioning different satellites to reach the receiver. System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations. GPS uses these "man-made stars" as reference points to calculate positions accurate to a matter of meters. In fact, with advanced forms of GPS you can make measurements to better than a centimeter! In a sense it's like giving every square meter on the planet a unique address. GPS receivers have been miniaturized to just a few integrated circuits and so are becoming very economical. And that makes the technology accessible to virtually everyone.
Technical description
The system consists of a "constellation" of at least 24 satellites in 6 orbital planes. The GPS satellites were initially manufactured by Rockwell; the first was launched in February 1978, and the most recent was launched November 6 2004. Each satellite circles the Earth twice every day at an altitude of 20,200 kilometers (12,600 miles). The satellites carry atomic clocks and constantly broadcast the precise time according to their own clock, along with administrative information including the Orbital elements of their own motion, as determined by a set of ground-based observatories.
The receiver does not need a precise clock, but does need to have a clock with good short-term stability and receive signals from four satellites in order to find its own latitude, longitude, elevation, and the precise time. The receiver computes the distance to each of the four satellites from the difference between local time and the time the satellite signals were sent (this distance is called a pseudo range). It then decodes the satellites' locations from their radio signals and an internal database. The receiver should now be located at the intersection of four spheres, one around each satellite, with a radius equal to the time delay between the satellite and the receiver multiplied by the speed of the radio signals. The receiver does not have a very precise clock and thus cannot know the time delays. However, it can measure with high precision the differences between the times when the various messages were received. This yields 3 hyperboloids of revolution of two sheets, whose intersection point gives the precise location of the receiver. This is why at least four satellites are needed: fewer than 4 satellites yield 2 hyperboloids, whose intersection is a curve; it is impossible to know where the receiver is located along the curve without supplemental information, such as elevation. If elevation information is already known, only signals from three satellites are needed (the point is then defined as the intersection of two hyperboloids and an ellipsoid representing the Earth at this altitude). The receiver contains a mathematical model to account for these influences, and the satellites also broadcast some related information, which helps the receiver in estimating the correct speed of propagation. High-end receiver /antenna systems make use of both L1 and L2 frequencies to aid in the determination of atmospheric delays.