Global Positioning System

1. Global Positioning System

2. What is GPS? • A worldwide radio wave-navigation system formed from a constellation of 24 satellites and their ground stations • GPS uses these “man-made stars” as reference points to calculate positions accurate to a matter of meters

3. GPS Constellation

4. Who Developed GPS? • U.S. Department of Defense spent $12 billion to create a super precise form of worldwide positioning • In the late days of the arms race, the U.S. military needed to be able to take out Russia’s missile system • That ability profoundly affected the balance of power

5. Pre – GPS • Sputnik launched in 1957 by Russia • Scientists at MIT learned they could track Sputnik’s orbit by listening to changes in its radio frequency as it came nearer or moved further away • First step in recognizing a location on earth could be determined using radio signals from the satellite

6. United State’s GPS • NAVSTAR – the official name of the U.S. Global Positioning System • First deployed satellites in the 1970s • The satellite completing NAVSTAR was deployed in the 1990s

7. NAVSTAR Satellite

8. Land vs. Sea • Russia’s nuclear system was on land • U.S. nuclear arsenal was largely at sea on submarines • For precise targeting, a system must have accurate launching coordinates as well as precise target coordinates • A submarine must surface and accurately fix its exact position quickly using GPS

9. GPS Signals • Originally for military purposes • The U.S. government/military could “fuzz” the signals which weakened the signal making it less accurate • Could also completely disable the signals to the public (& other countries!) through encryption

10. Ground Control Segments • Also known as Control Segments • Check both the operational health and exact position of satellite in space • Transmit corrections • Five Ground Control Segments: Hawaii, Ascension Island, Diego Garcia, Kwajalein, and Colorado Springs

11. Land Control Segments

12. How Does GPS Work • Satellites broadcast radio signals to Earth with information about their location and the exact time the signal was transmitted (each satellite carries an atomic clock).

13. How it Works, continued • By calculating the difference between radio signals received from four or more satellites(originally used 3 for triangulation), GPS receivers on the ground can determine their own location (latitude/longitude), and elevation with great accuracy.

14. Civilian Demand • Civilian demand for GPS products surged in 2000 when military stopped “fuzzing” signals • Overnight, navigation devices became 10 times more accurate

15. Civilian Uses • Fishing to freight to fleet tracking • Navigation (cars, train, boats, planes) • ONSTAR, emergency vehicles • In phones, wristwatches & dog collars • Geocaching – 800,000 active "caches” • Construction, moviemaking, farming equipment

16. Scientific Use • Meteorologists gauge wind speed and other variables • Zoologists track endangered species • Geologists study earthquakes • Technicians synchronize computer networks for power grids to financial networks

17. Effects on Economy • GPS receivers have been miniaturized to just a few integrated circuits, thus cheaper • Worldwide GPS market will total $75 billion by 2013 • 100,000 jobs

18. Updating NAVSTAR • Satellites are regularly replaced as they age and fail • As of 2009 there are currently more than 30 in space • Extras used as spares and backups • Updating signals/frequencies to work with other systems

19. Russia’s GLONASS • First satellite deployed in 1970s • Operational in the 1990s • 21 satellites originally + 2 from India • Can disable use by others through encryptions • All ground control segments are located within the former Soviet Union

20. Europe’s GNSS • Galileo should be operational sometime between 2010-2013 • Full precision for military and civilian use • Will have 30 satellites • Bases in Germany and Italy

21. Galileo goes International • Created by European Union(27 members) • China, Israel, Ukraine, Morocco, South Korea, Norway joined efforts with Galileo • Neutral technology available to everyone

22. Galileo’s Services • Open Service – free • Commercial Service – more accuracy, encrypted, available for a fee • Public Regulated Service – law enforcement, military, security • Safety of Life Service – safety/critical transport, air traffic control

23. U.S. Concerns • Initial frequency chosen for Galileo made it impossible to block without interfering with NAVSTAR • Galileo agreed to use a different frequency allowing NAVSTAR to be jammed for national security • NAVSTAR in conjunction with GALILEO is very accurate

24. Websites • http://web.haystack.mit.edu/pcr/whereami/documents/gpstutorial.htm • http://www.trimble.com/gps/index.html • http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html • http://www.spaceandtech.com/spacedata/constellations/glonass_consum.shtml