This presentation provides an overview of the Global Positioning System (GPS). It discusses the three segments of GPS: the control segment composed of ground stations that monitor the satellites, the space segment of 24 satellites orbiting Earth, and the user segment of GPS receivers. It describes how GPS determines position based on calculating the time difference of signals from multiple satellites. Sources of error and signal interference are also reviewed. Applications of GPS include navigation, mapping, tracking, and timing systems.

1. WELCOME

2. INSTITUTE OF TECHNOLOGY
& MANAGEMENT
PRESENTATION ON
GPS
PREPARED BY : KUNAL PRAKASH MISHRA
ECE 4’th YR.

3. CONTENTS
 Introduction
 Working
 Different segments of GPS
 Primary function of GPS
 GPS position location principle
 PSEUDO RANDOM NOISE code
 Equations involved
 Sources of signal interference
 GPS receiver
 DGPS
 Applications of GPS

4. INTRODUCTION
It is global positioning system used for position
location & navigation.
It is a network of 24 NAVSTAR satellites orbiting
around earth at an altitude of approx. 20200 kms.
In this system satellites are placed in MEO
It consists of satellites ,receivers & ground
control systems.
It is operated on L –band frequency(1-2GHz).
A GPS works in any weather condition

5. contd…
It provides a direct readout of the present
position of a GPS receiver with a typical accuracy
of 30 m.
The orbital period of a satellite is approx. one-
half a sidereal day (11hr 58 min)
LORAN is also used for position location
There are three segments of a GPS & they
are:
1. Control segment
2. Space segment
3. User segment

6. CONTROL SEGMENT
A control segment is composed of :
1.A master control station
2.Four dedicated ground stations
3.Six dedicated monitor stations

7. Three Segments of the GPS
Space Segment
User Segment
Control Segment
Ground
Antennas
Master Station Monitor Stations

8. Control Segment
US Space Command
Cape Canaveral
Hawaii
Kwajalein Atoll
Diego Garcia
Ascension
Is.
Master Control Station Monitor Station Ground Antenna

9. Space Segment

10. User Segment
 Military.
 Search and rescue.
 Disaster relief.
 Surveying.
 Marine, aeronautical and terrestrial navigation.
 Remote controlled vehicle and robot guidance.
 Satellite positioning and tracking.
 Shipping.
 Geographic Information Systems (GIS).
 Recreation.

11. Four Primary Functions of GPS
 Position and coordinates.
 The distance and direction between any two
waypoints, or a position and a waypoint.
 Travel progress reports.
 Accurate time measurement.

12. Position is Based on Time
Radio waves travel at the speed
of light. If GPS signal leaves
satellite at time “T”…
T
…and is picked up by the
T+3 receiver at time “T + 3.”
Then distance between
satellite and receiver = “3
times the speed of light”

13. Pseudo Random Noise Code
Time
Difference
Satellite PRN
Receiver PRN

14. GPS RECEIVER

15. Signal From One Satellite
The receiver is
somewhere on
this sphere.

16. Signals From Two Satellites

17. Three Satellites (2D Positioning)

18. Triangulating Correct Position

19. Three Dimensional (3D) Positioning

20. Sources of GPS Error
Standard Positioning Service (SPS ): Civilian Users
Source Amount of Error
 Satellite clocks: 1.5 to 3.6 meters
 Orbital errors: < 1 meter
 Ionosphere: 5.0 to 7.0 meters
 Troposphere: 0.5 to 0.7 meters
 Receiver noise: 0.3 to 1.5 meters
 Multipath: 0.6 to 1.2 meters
 User error: Up to a kilometer or more
Errors are cumulative

21. Sources of Signal Interference
Earth’s Atmosphere
Solid Structures
Metal Electro-magnetic Fields

22. Ideal Satellite Geometry
N
W E
S

23. Good Satellite Geometry

24. Poor Satellite Geometry
N
W E
S

25. Poor Satellite Geometry

26. Real Time Differential GPS
x+5, y-3
x+30, y+60
x-5, y+3
Receiver DGPS Receiver
DGPS Site
DGPS correction = x+(30-5) and True coordinates =
y+(60+3) x+0, y+0
True coordinates = x+25, y+63 Correction = x-5, y+3

27. A visual example of the GPS constellation in motion
with the Earth rotating. Notice how the number of
satellites in view from a given point on the Earth's
surface, in this example at 45°N, changes with time.

28. APPLICATION
GPS has become a widely used & useful tool for
commerce, scientific uses , tracking &
surveillance.
1.Surveying
2.map-making
3.Navigation
4.Cellular telephony
5.Tectonics( fault motion measurement in
earthquakes)
6.Geofencing (vehicle ,person tracking
systems)
7. Military

29. Any query ???