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1. ELA 12021
Assignment 01
R.M.G.Viranga
SEU/IS/09/PS/109

3. Global Positioning
System
GPS

4. contents
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What is GPS?
The network of satellite
How it works?
Triangulation
GPS Elements
GPS Devices
How accurate is GPS?
GPS Signals
The GPS satellite system
Sources of GPS signal errors
Advanced Technology in GPS

5. What is GPS?
•The Global Positioning System (GPS) is a
satellite-based navigation system.
•It is made up of a network of 24 satellites
placed into orbit by the U.S. Department of
Defense.
•It was originally intended for military
applications.
•In 1980s, the government made the system
available for civilian use.
•GPS works in any weather
conditions, anywhere in the world, 24 hours a
day.

6. The network of satellite

7. How it works?
•GPS satellites circle the earth twice a day in a
very precise orbit and transmit signal
information to earth .
•GPS receivers take this information and use
triangulation to calculate the user's exact
location.
•Using the time difference between the signal
was transmitted by a satellite and with the time
it was receive, the GPS receiver can determine
the user's position and display it on the unit's
electronic map.

8. How it works?

9. Triangulation

10. GPS Elements
• GPS elements consist of three basic parts.
• They are,
• Space segment
• User segment
• Control segment

11. Space segment
• Space segment of the system consist of the
GPS satellites.
• These space vehicles (vs.) send radio signal
from space.
• The nominal GPS operation constellation
consist of 24 satellites that orbit the Earth in
12 hours.

12. User segment
• User segment consist of receivers, which you
can hold in your hand or mount in your
path.
• . The GPS receiver converts SV signals into
position, velocity and time.
• GPS receivers are used for
navigation, position, time and other
research.

13. Control segment
• Control segment consist of a system of
tracking stations located around the world.
• These stations measure signals from the sves
which are incorporated into orbital model
for each satellites.
• The master control facility determines the
orbit and clock parameters using
measurements from five monitor stations
distributed around the world.

14. GPS Devices

15. How accurate is GPS?
•Today's GPS receivers are extremely
accurate, because of their parallel multi-channel
design.
•Garmin® GPS receivers are accurate to within 15
meters on average.
•But certain atmospheric factors and other
sources of error can affect the accuracy of GPS
receivers.

16. GPS Signals
•The Differential GPS (DGPS) system consists of
a network of towers that receive GPS signals and
transmit a corrected signal by beacon
transmitters.
•In order to get the corrected signal, users must
have a differential beacon receiver and beacon
antenna in addition to their GPS.

17. The GPS satellite system
• 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. and
are travelling at speeds of roughly 7,000
miles an hour.
• GPS satellites are powered by solar energy.

18. GPS satellite

19. Sources of GPS signal errors
• The satellite signal slows as it passes through
the atmospheric layers of Ionosphere and
troposphere.
• Signal multipath occurs when the GPS signal
is reflected off objects such as tall buildings
or large rock surfaces before it reaches the
receiver.
• Number of satellites visible.
• Satellite geometry/shading .
• Intentional degradation of the satellite
signal.

20. Signal multipath

21. Advanced Technology in
GPS
• Differential Global Positioning System (DGPS)
• Local Area Augmentation System (LAAS)
• Wide Area Augmentation System (WAAS)
• Nation Wide Differential GPS (NDGPS)
• High Accuracy Nation Wide Differential GPS (HANDGPS)

22. summery
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•
•
•
What is GPS?
The network of satellite
How it works?
Triangulation
GPS Elements
GPS Devices
How accurate is GPS?
GPS Signals
The GPS satellite system
Sources of GPS signal errors
Advanced Technology in GPS

23. Thank You