Short Note on GPS

GPS (Global Positioning System) is a satellite-based navigation system which was created by U.S. Department of Defence as a part of NAVSTAR satellite program. It gives geolocation and time information to a GPS receiver in all climate conditions, anywhere on or close to the Earth where there is an unobstructed line of sight to four or more GPS satellites.

Global Positioning System Example: Automobile tracking – utilized to identify, locate and maintain contact reports with a number of vehicles in real-time.

Write a Short Note on GPS (Global Positioning System)

GPS has three segments:

  1. Space segment
  2. Control segment
  3. User segment

The space segment is made up of at least 24 satellites with are placed on six circular orbital planes (Four satellites per one orbit). Each orbit is inclined at an angle of 55° relative to equator plus they are separated by 60°.  Satellites are at an altitude of approximately 20,200km (12,600 mi).

As of 2016, there are actually thirty-two satellites in the GPS constellation, thirty-one of which are in use. Every satellite requires 11 hours and 56 minutes to circle the earth. The extra satellites enhance the accuracy of GPS receiver calculations by giving redundant measurements. Considering the increased number of satellites, the constellation was changed to a nonuniform set up.

Short Note on GPS - Global Positioning System

The control segment handles synchronizing satellite’s atomic clocks and adjusts the ephemeris of each and every satellite’s inner orbital model. It is maintained by U.S. Air Force.

User segment is for typical users (like civil, commercial, scientific, military users, etc.) that want to make use of GPS receivers to estimate their position.

What is GPS used for ?

At present, GPS is a multi-use, space-based radio navigation system belonging to the united states government and controlled by the US Air Force to meet national defense, homeland security, civil, commercial, and scientific requirements.

How Global Positioning System Works ?

GPS satellites circle the Earth 2 times a day in a precise orbit. GPS position is determined using data coming from satellites. GPS receiver computes distance to satellites and using theirs position calculate its own.

To find out the distance to satellites receiver will need to have very precise clock. This is the primary reason why each satellite comes with an atomic clock and all those clocks should be synchronized. In this system the weakest part is the GPS receiver since it has only the quartz clock and require time synchronization.

In these modern times, GPS receivers have the ability to receive from 12 to 20 satellite signals and make use of them to estimate the position.


  1. Michael Amartey says

    Who brought the idea of the gps

  2. can we call errors to do with satellites,gross errors?

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