1. Instructed on: 24-Feb-2011 | Session: #06
GPS
By: Mohanad Yehia
Topic Code: TCW-05-2012
All Copy Rights Saved to the 7th Students’ Conference on Communication and Information Based in the Faculty of Computers and Information Cairo University – Egypt 2011/2012 www.scci-cu.com
3. What is GPS?
• Global Positioning System.
• Worldwide navigation system formed of 31
satellites and their ground stations.
• Maintained by the United States government
and is freely accessible by anyone with a GPS
receiver.
4. Other systems
• The Russian GLObal NAvigation Satellite
System (GLONASS) .
• European Union Galileo positioning system.
• Chinese Compass navigation system.
• Indian Regional Navigational Satellite System.
5. History of GPS
• The GPS project was developed in 1973 to
overcome the limitations of previous
navigation systems.
• GPS was created and realized by the U.S.
Department of Defense and was originally run
with 24 satellites.
6. History of GPS
• In 1983, after Soviet interceptor aircraft shot
down the civilian airliner KAL 007 that strayed
into prohibited airspace because of
navigational errors, killing all 269 people on
board, U.S. President Ronald
Reagan announced that GPS would be made
available for civilian uses once it was
completed.
7. History of GPS
• Full Operational Capability was declared by Air
Force Space Command in April 1995.
• In 1996, recognizing the importance of GPS to
civilian users as well as military users, U.S.
President Bill Clinton issued a policy declaring
GPS to be a dual-use system.
8. History of GPS
• In November 2004, QUALCOMM announced
successful tests of assisted GPS for mobile
phones.
• The oldest GPS satellite still in operation was
launched on November 26-1990 while the
newest GPS satellite was launched on July 16-
2011.
9. How GPS works
1. Trilateration.
2. Measuring distance.
3. The perfect timing.
4. Position of satellites.
11. 1-Trilateration
Trilateration methods involve the determination
of absolute or relative locations of points by
measurement of distances, using
the geometry of spheres or triangles.
12. 2-Measuring distance
GPS receiver measures distance using the travel
time of radio signals sent from satellites.
example:
Velocity (60 mph) x Time (2 hours) = Distance
(120 miles).
13. 3-The perfect timing
• On the satellite side, timing is almost perfect
because they have incredibly precise atomic
clocks on board.
• If their timing is off by just a thousandth of a
second (at the speed of light) that translates
into almost 200 miles of error
14. 4-Position of satellites
• The GPS receivers know the exact location of
the satellites in range from the received radio
signal.
• The basic orbits are quite exact but just to
make things perfect the GPS satellites are
monitored by the Department of Defense.
