Global Positioning System

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ABSTRACT

The Global Positioning System (GPS) is a U.S. space-based global navigation satellite system. It provides reliable positioning, navigation, and timing services to worldwide users on a continuous basis in all weather, day and night, anywhere on or near the Earth which has an unobstructed view of four or more GPS satellites. GPS uses principles of general relativity to correct the satellites' atomic clocks. GPS is made up of three segments: Space, Control and User. GPS satellites broadcast signals from space that GPS receivers use to provide three-dimensional location (latitude, longitude, and altitude) plus precise time. The position calculated by a GPS receiver requires the current time, the position of the satellite and the measured delay of the received signal. The position accuracy is primarily dependent on the satellite position and signal delay. The Global Positioning System, while originally a military project is considered a dual-use technology, meaning it has significant applications for both the military and the civilian industry. GPS based time reference provides inexpensive but highly-accurate timing and synchronization capability and meets requirements in locating, monitoring, and control. In the present era of restructuring and modernization, the applications of GPS technology in various industry are growing and covering several technical and management activities. Therfore it is necessary to remove the GPS signal errors.

INDEX

SR.NO| CONTENTS|
1.| ABSTRACT|
2.| INTRODUCTION TO GPS|
3.| HISTORY OF GPS|
4.| GPS SIGNAL|
5.| SYSTEM SEGMENTATION|
6.| WORKING OF GPS|
7.| GPS IN INDIA|
8.| NAVIGATION DEVICES & SOFTWARES|
9.| ADVANTAGES & DISADVANTAGES|
10.| APPLICATIONS & LIMITATIONS|
11.| CONLUSION|
12.| REFERENCES|

Introduction to global positioning system

GPS is an acronym that stands for ‘Global Positioning System’. It is a U.S. space-based global navigation satellite system. It provides reliable positioning, navigation, and timing services to worldwide users on a continuous basis in all weather, day and night, anywhere on or near the Earth which has an unobstructed view of four or more GPS satellites. The system was devised by the US Department of Defense and is open for use to anyone who wishes to use it. Basically, it uses satellites that were sent into space, determining their current location based on the signals the satellites continually send to the GPS device. At the moment, there are over 30 GPS satellites in service; however, to determine the location of any one GPS device, taking into account the signals of four of those satellites is enough. GPS is made up of three segments: Space, Control and User. The Space Segment is composed of 24 to 32 satellites in Medium Earth Orbit and also includes the boosters required to launch them into orbit. The Control Segment is composed of a Master Control Station, an Alternate Master Control Station, and a host of dedicated and shared Ground Antennas and Monitor Stations. The User Segment is composed of hundreds of thousands of U.S. and allied military users of the secure GPS Precise Positioning Service, and tens of millions of civil, commercial and scientific users of the Standard Positioning Service GPS satellites broadcast signals from space that GPS receivers use to provide three-dimensional location (latitude, longitude, and altitude) plus precise time.

History
The idea of having a satellite navigation system dates back to 1960 already. This was when the first such system, Transit, which was used by the US Navy, was tested successfully. At the time, it used only five satellites. Approximately once an hour, it would tell you where you were thanks to those five satellites. Approximately ten years later, in the 1970s, the first worldwide radio navigation system was...
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