1. Global Positioning Systems A HISTORY OF THE U.S.A. GPS

2. Navigation  Mankind has always needed a way to:  calculate where he IS on the earth  calculate where he is GOING  Old ways included  “dead reckoning”, landmarks,  observing the sun, moon, and stars  Who wants to be lost:  at sea, in the desert, in the cold or heat,  in a war zone,  or just out hiking?

3. What is GPS?  A space based radio-navigation system used to calculate location (latitude/longitude/elevation)  accurate to a matter of meters  Consists of:  a constellation of satellites  Originally 24, currently 30+  Along with FIVE ground control stations

4. Common Man’s Use  GPS available in:  cars, boats, planes, laptops, cell phones  construction equipment  movie making gear  farm machinery  GPS receivers:  miniaturized with integrated circuits  thus becoming very economical  Making GPS use accessible to all

5. Who Developed GPS?  U.S. Department of Defense  spent $12 billion  creating precise form of worldwide positioning  When/why  in the late days of the nuclear arms race  ability to take out Russia’s missile system  Result:  profoundly affected the balance of power in USA’s favor

6. USA vs. Russia  Space Race  Russia launched Sputnik in 1957  Who would control outerspace?  In response USA started NASA in 1958  Put man on the moon in 1969  Nuclear Arms Race  USA had superior nuclear propelled submarines  Could go to great ocean depths  Hard to be detected by Russian radar  Carried nuclear weapons  For precise targeting,  must have accurate launching coordinates  as well as precise target coordinates

7. How Does GPS Work?  The basis of GPS is “triangulation”  To triangulate:  GPS receiver measures distance from 3 satellites  uses the travel time of radio signals to measure distance  if distance is calculated from more than 3 satellites, even more accurate  To measure travel time, GPS needs:  very accurate timing (atomic clocks)  location of satellites (built in)  corrections for delays as signal travels through the atmosphere

8. Disturbances in Signals  In the ionosphere  ionized particles (+ atoms) exert a perturbing effect on signals  In the troposphere  water vapor,  variances in atmospheric temperature  Variances in atmospheric pressure

9. GPS Master Plan  Launch of the 24th block II satellite  in March 1994  completed the GPS constellation  Four additional satellites  in reserve to be launched “on need”  Spacing of satellites  minimum of five satellites are in view  from every point on the globe

10. GPS Constellation

11. Satellites (Example)  Name: NAVSTAR  Manufacturer: Rockwell International  Altitude: 10,900 nautical miles  Size: 17 ft. with solar panels extended  Orbital Period: 12 hours  Orbital Plane: 55 degrees to equatorial plane  Lifespan: 7.5 years  Current constellation: 24 Block II production satellites

12. NAVSTAR Satellite

13. Ground Stations  Also known as the Control Segments  Control Segments check both the:  operational health and  exact position of satellites in space  Transmit corrections  Controlled by the U.S. Air Force  Five Control Segment Stations:  Hawaii, Ascension Island, Diego Garcia,  Kwajalein, and Colorado Springs

14. Land Control Segments

15. Points of Interest  What ways can you think of using GPS in our daily lives?  What is the future of GPS?  What careers would be related?  Do other countries have their own GPS?  Can they use ours?  Can we access theirs?  Civilian vs. military use?