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  1. 1. ELA 12021 Assignment 01 R.M.G.Viranga SEU/IS/09/PS/109
  2. 2. Global Positioning System GPS
  3. 3. contents • • • • • • • • • • • 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
  4. 4. 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.
  5. 5. The network of satellite
  6. 6. 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.
  7. 7. How it works?
  8. 8. Triangulation
  9. 9. GPS Elements • GPS elements consist of three basic parts. • They are, • Space segment • User segment • Control segment
  10. 10. 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.
  11. 11. 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.
  12. 12. 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.
  13. 13. GPS Devices
  14. 14. 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.
  15. 15. 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.
  16. 16. 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.
  17. 17. GPS satellite
  18. 18. 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.
  19. 19. Signal multipath
  20. 20. 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)
  21. 21. summery • • • • • • • • • • • 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
  22. 22. Thank You