The document discusses the Global Positioning System (GPS). It describes how GPS works using a network of 24 satellites orbiting Earth. GPS satellites continuously transmit radio signals that allow GPS receivers to calculate their precise location by triangulating signals from at least four satellites. The key components of GPS are the control segment consisting of ground stations that monitor the satellites, the space segment of satellites orbiting in space, and the user segment of GPS receivers used to locate positions. Some applications of GPS include navigation, tracking, and scientific uses.

1. S.JANANI
IV ECE

2.  Introduction
 The GPS satellite system
 Working of GPS
 Components of a GPS
 Applications
 Advantages and disadvantages
 Conclusion

3.  GPS was created and realised by US
department of defence(USDOD).
 GPS is a space-based global navigation
satellite(GNSS).
 Used for reliable location and time
information.
 It works in all weather conditions and all
times and day where on or near the earth.

4.  There is no subscription fee and setup
charges to use GPS.
 GPS is a useful tool for Commerce,Scientific
uses,Tracking and surveillance.

5.  GPS system is made up of a network of 24
satellites placed into the orbit by the US.
 It is placed 20,000 Km above the earth.
 Travelling speed is roughly 7,000 miles per
hour.
 It’s lifetime is about 10 years and the
replacement are constantly being built and
launched into the orbit.

6.  Satellite weight is about 2,000 pounds and it
is 17 feet across the solar panels extended.
 It is powered by solar panels.
 They also have back up batteries onboard to
keep them running even in solar eclipse
time,where there is no solar power.
 Small rocket boosters on each satellite keep
them flying in correct path(station keeping).

7.  The goal of GPS is to determine the User’s
position on earth in three dimensions:east-
west,north-south and vertical.
 GPS uses satellites and computers to
compute positions anywhere on earth.
 It is based on satellite ranging.
 Basic formula used in this process is
Distance=speed * Time.

10. Geometric Principle:
You can find one’s location if you know
its distance from other, already-known
locations.
Things which need to be determined:
 Time taken by the signals to reach the GPS
receiver.
 The Distance Between Receiver’s Position and
the GPS Satellites.

11.  SATELLITE RANGING – determining the
position on the earth by measuring the
distance from a group of satellites in space
to the receiver.
 To determine user’s position signals we use
four overhead satellites to determine it’s
position and the time of emission of the
signal.

12. GPS receivers store this orbit information
for all of the GPS satellites.
A GPS receiver can tell its own position
by using the position data of itself, and
compares that data with 3 or more GPS
satellite.
 By measuring the amount of time taken by
radio signal (the GPS signal) to travel from
the satellite to the receiver.

13.  GPS receiver has built in microprocessor to
display the location of the user.
 The user’s position is displayed on the unit’s
electronic map.

14.  Three major components of GPS are given
below.
 The control segment.
 The space segment.
 The user segment.

15.  The CS consists of following entities:
 Monitor Stations
 Ground Antennas
 Powered by solar cells.
 GPS satellites fly in circular orbits at an
altitude of 20,200 km.

16.  Falcon Air Force Base in Colorado.
 Cape Canaveral.
 Florida.
 Hawaii.
 Ascension Island in the Atlantic Ocean.
 Diego Garcia Atoll in the Indian Ocean.
 Kwajalein Island in the South Pacific Ocean.

17.  Ground antennas monitor and
Track the satellites from
horizon to horizon.
 They also transmit correction information to
individual satellites.
 Communicate with the GPS satellites for
command and control purposes.

18.  The space segment is composed of 24 to 32
satellites in MEO.
 Contains payload adaptors to the boosters
required to launch them into the orbit.

19.  GPS receivers are generally
Composed of
1.An antenna( tuned to the frequencies
transmitted by the satellites),
2.Receiver-processors, and
3.Highly-stable clock( commonly a crystal
oscillator).
 They can also include a display for showing
location and speed information to the user.

20.  Surveying : Surveyors use
absolute locations to make
maps and determine
boundaries.
 Missile and Propulsion
guidance.

22.  Tectonics:GPS enables direct fault motion
measurements in earth quakes.
 Navigation.
 Target tracking.
 Missile guidance.
 Search and rescue.
 Remote sensing.

23.  Materials used to manufacture GPS are
affordable.
 GPS can provide worldwide, three-
dimensional positions, 24 hours a day, in any
type of weather.
 It uses one way transmission,hence GPS
transmitter is not needed.
 Size is small.

24.  There must be a relatively clear "line of
sight" between the GPS antenna and four or
more satellites.
 Difficulties may occur while tracking in urban
areas.
 The GPS constellation, like manmade stars in
the sky, can be used for guiding and
navigation.