Wednesday, April 4, 2007

Global Positioning Systems

We generally wish to locate a particular object at an ease.New technology takes us to great heights with which we can exactly locate an object on earth.This is only know as Global Positioning System.

WHAT IS GLOBAL POSITIONING SYSTEM?
An acronym for Global Positioning System.A worldwide radio-navigation system that was developed by the US. Department of Defense.In addition to military purposes it is widely used in marine, terrestrial navigation and location based services.

WHO USES GPS?

GPS has a variety of applications on land, at sea and in the air.GPS is also typically used for navigation by recreational boaters, commercial fishermen, and
professional mariners. Land-based applications are more diverse.Surveyors use GPS for an increasing portion of their work.GPS is now commonplace in automobiles as well. Some basic systems are in place and provide emergency roadside assistance at
the push of a button (by transmitting your current position to a dispatch center).

HOW GPS WORKS?

A constellation of 24 satellites orbiting the earth at a very high altitude. GPS satellites transmit signals that allow one to determine, with great accuracy, the locations of GPS receivers.The receivers can be fixed on the Earth, in moving vehicles, aircraft, or in low-Earth orbiting satellites. GPS is used in air, land and sea navigation, mapping, surveying and other applications where precise positioning is necessary.GPS receivers take this information and use
triangulation to calculate the user's exact location.

GPS SIGNAL RECEIVING DEVICES.

There are many sophisticated devices which are specially manufactured for navigation using GPS systems.Now a days we can get mobiles which are GPS enabled.We can even search for ATM in our location using GPS phones.These devices generally have a color display which shows the roads and places.All the ambulances are enabled with GPS
systems in order to serve in case of emergency.Figuring out how to fold maps is a
problem of the past. Compasses are passe. Portable GPS devices, fitting into the palm of your hand or built into automobile dashboards, now bring Space Age navigation to the masses

IS GPS ACCURATE?

Today's GPS receivers are extremely accurate,thanks to their parallel multi-channel design.Newer GPS receivers with WAAS (Wide Area Augmentation System) capability can improve accuracy to less than three meters on average.Offcourse there is a chance of occuring signalling errors in GPS systems.We shall se those errors..

SATELLITE SYSTEM IN GPS.

The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,000 miles an hour.

GPS SIGNAL ERRORS.

Here are some sources of GPS signalling errors..
- Ionosphere and troposphere delays
- Signal multipath
- Receiver clock errors

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