GPS

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GPS

  1. 1. GPS
  2. 2. What is GPS? <ul><li>GPS is a space based all weather radio navigation system. </li></ul>
  3. 3. GPS <ul><li>Provides </li></ul><ul><li>Position (geographic), Velocity & Time (PVT) Quickly, Economically And Precisely 24 hours a day, anywhere in the world under the sky </li></ul>
  4. 4. Components of GPS <ul><ul><ul><ul><ul><li>Space segment </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Control segment </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>User segment </li></ul></ul></ul></ul></ul>
  5. 5. Salient steps <ul><li>The receiver picks up the signals from the satellites; </li></ul><ul><li>Uses signal travel time to calculate distance to the satellites </li></ul><ul><li>Using Analytical Principle, position of the receiver gets calculated. </li></ul>
  6. 6. Space segment <ul><li>24 satellites </li></ul><ul><li>Orbit every 12 hours at 20,200 kms </li></ul><ul><li>4 satellites in each of 6 orbital planes </li></ul><ul><li>Transmit a uniquely coded radio signal </li></ul><ul><li>Equipped with onboard atomic standard </li></ul>
  7. 7. What is so special about an 20200 km orbit? <ul><li>‘ Orbits’ twice per day </li></ul><ul><li>Large ‘viewable’ area </li></ul>
  8. 8. Positioning With Satellite <ul><li>Satellites are reference points to locations on earth (their location are known) </li></ul><ul><li>A location of a point on earth is identified by “triangulation” </li></ul><ul><li>Travel time of each signal is determined </li></ul><ul><li>Signals travel at Speed of light </li></ul><ul><li>Distance = Travel Time * Speed of Light </li></ul>
  9. 9. Principle of working using GPS <ul><li>The basis of GPS technology is precise measurement of time; </li></ul><ul><li>Use of orbiting satellite position to find location of receiver by method of resection </li></ul>
  10. 10. Pseudoranging
  11. 11. S 1 (x 1 ,y 1 ,z 1 ) S 2 (x 2 ,y 2 ,z 2 ) S 3 (x 3 ,y 3 ,z 3 ) S 4 (x 4 ,y 4 ,z 4 ) GPS Receiver  1 =  {(x 1 -x) 2 +(y 1 -y) 2 +(z 1 -z) 2 } + c. Δ t  2 =  {(x 2 -x) 2 +(y 2 -y) 2 +(z 2 -z) 2 } + c. Δ t  3 =  {(x 3 -x) 2 +(y 3 -y) 2 +(z 3 -z) 2 } + c. Δ t  4 =  {(x 4 -x) 2 +(y 4 -y) 2 +(z 4 -z) 2 } + c. Δ t Principle of GPS Positioning (X,Y,Z)
  12. 12. Control segment <ul><li>Ground-based monitoring and upload stations </li></ul><ul><li>Control orbit and timing information </li></ul>
  13. 13. USER It includes all GPS users. User can receive the GPS signals through antenna connected to the receiver and can determine its position on the surface of the earth
  14. 14. User segment <ul><li>GPS Receivers; </li></ul><ul><li>Compatible software for Planning, Downloading and Processing of GPS receiver data; </li></ul>
  15. 15. Some Applications of GPS
  16. 16. Some Applications of GPS
  17. 17. Some Applications of GPS
  18. 18. Some Applications of GPS
  19. 19. GPS Receivers (contd.) Navigation <ul><li>capable of about 12 meter accuracy </li></ul><ul><li>light-weight, cheap! </li></ul><ul><li>navigation applications </li></ul>
  20. 20. GPS data processing software <ul><li>Real time </li></ul><ul><li>Post-processing </li></ul>
  21. 21. GPS SIGNAL <ul><li>CARRIER, f(t) </li></ul><ul><li>CODE, C(t) </li></ul><ul><li>NAVIGATIONAL DATA, D(t) </li></ul>
  22. 22. CARRIERS <ul><li>L1 (154 f or 1575.42 MHz) </li></ul><ul><li>L2 (120 f or 1227.60 MHz) </li></ul>
  23. 23. GPS Coordinate system <ul><li>World Geodetic System, 1984 (WGS84) </li></ul>
  24. 24. GPS receivers Positioning Techniques <ul><ul><li>Absolute </li></ul></ul><ul><ul><li>Relative </li></ul></ul><ul><ul><ul><li>Real Time </li></ul></ul></ul><ul><ul><ul><li>Post-processing </li></ul></ul></ul>
  25. 25. LIMITATIONS <ul><li>Ionospheric delay correction is not possible to compute </li></ul><ul><li>Weak signal – not available under canopy or under shed </li></ul><ul><li>Susceptible to interference </li></ul>
  26. 26. GPS is getting popular as a means for collection of data
  27. 27. GPS DATA <ul><li>Reliable </li></ul><ul><li>Accurate </li></ul><ul><li>Real-time </li></ul>
  28. 28. GPS <ul><li>Can be used in any conceivable situation </li></ul><ul><li>Under the sky </li></ul><ul><li>Where the exact position of any object or phenomena involved . </li></ul>
  29. 29. <ul><li>Thank You </li></ul>

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