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Global positioning system ppt
- 1. Global Positioning System Presented by: Sushant Maurya ECE/27/2013
- 2. CONTENTS Introduction History Need of GPS How does the GPS work? Factors that affect the GPS Applications Future Scope Conclusion References
- 3. INTRODUCTION The Global Positioning System(GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defence that continuously transmit coded information, which makes it possible to precisely identify locations on earth.
- 4. HISTORY In the old time, people have used Stars and moon to get positions so that they can travel..
- 5. NEED OF GPS Where am I? Where am I going? Where are you? What is the best way to get there? When will I get there? GPS technology can answer all these questions.
- 6. WHERE IT CAME FROM Funded and Controlled by U.S. DOD Originally Designed for the Military 1978 First Block of Satellites launched 1989 Second Block of Satellites launched 1995 Fully Operational Korean Flight 007 Crashed(1983)– President Ronald Regan guaranteed all GPS signals would be available to the world
- 7. HOW DOES THE GPS WORK? Triangulation from satellite Distance measurement through travel time of radio signals Very accurate timing required Along with distance, need to know exactly where the satellites are in space Finally delays have to be corrected
- 8. THREE SEGMENTS OF GPS
- 9. SPACE SEGMENT 24 Satellites in 6 orbital plane 4 satellites in each plane 20,200km altitudes Five to Eight Satellites visible at any time Each satellite transmits data including both current location and time
- 10. CONTROL SEGMENT
- 11. USER SEGMENT GPS Receivers • Decodes the signals from Satellites. • Calculate the distance. • Triangulates the position • Triangulation?
- 12. CALCULATING DISTANCE Velocity x Time = Distance Radio waves travel at the speed of light, roughly 3,00,000km per second (kmps) If it took 0.06 seconds to receive a signal transmitted by a satellite floating directly overhead, use this formula to find your distance from the satellite. 3,00,000kmps x 0.06 seconds = 18,000km
- 13. TRIANGULATION(IN 2D) A man says that he is at 500km from Delhi.
- 15. TRIANGULATION(IN 2D) A man says that he is at 500km from Delhi. Again he says, he is at 300km from Lucknow.
- 17. TRIANGULATION(IN 2D) A man says that he is at 500km from Delhi. Again he says, he is at 300km from Lucknow. He again says that he is 400km away from Jaipur.
- 19. TRIANGULATION(IN 3D) For 3D , we need at least 4 known points or 4 satellites.
- 24. Standard Positioning System • Data Transmitted on L1(1575.42 MHz) Frequency • For civil users • Accuracy is degraded Precise Positioning System • Data Transmitted on L1(1575.42 MHz) and L2(1227.60 MHz) Frequencies • For Military users • Highly Accurate Modes of Operation HA=100m VA=156m TA=340ns HA=22m VA=27.7m TA=200ns
- 25. FACTORS THAT AFFECT GPS Clock Error Relativity Error Multipath - reflection of GPS signals near the antennae Ionosphere - change in the travel time of the signal Troposphere - change in the travel time of the signal Satellite Geometry - general distribution of the satellites Satellite Health - Availability of Signal Radio Frequency (RF) Interference
- 26. MULTIPATH Sometimes the signals bounce off things before they hit the receivers.
- 27. Sources of Signal Interference Earth’s Atmosphere Solid Structures Metal Electro-magnetic Fields
- 28. SATELLITE GEOMETRY When the satellites are all in the same part of the sky, readings will be less accurate. PDOP-Position Dilution of Precision
- 29. CLOCK ERROR Time of the satellites and receivers must be synchronized. GPS satellites use Atomic Clocks. Most of the GPS receivers do not use Atomic clock because of expense. So we get error in time , so error in position.
- 30. RELATIVE ERROR According to Special Relativity- on-board atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day because of the slower ticking rate due to the time dilation effect of their relative motion. Means satellite clock=T-7us
- 31. RELATIVE ERROR Contd. According to General Relativity-clocks closer to a massive object will seem to tick more slowly than those located further away. A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day. Means satellite clock=T+45us On combining both. Time =T+45-7=T+38us.
- 32. RELATIVE ERROR Contd. 38us means error of 11 km per day To overcome this error , satellite clock is corrected generally after 2-4 hour.
- 34. APPLICATIONS Contd.. Military • Intelligence & Target Location • Navigation • Weapon Aiming & Guidance Transportation • Aviation • Fleet Tracking • Marine
- 35. WORLD WORK ON NAVIGATION GPS –by United States GLONASS -by Russian GALILEO-by European Union Compass –by China IRNSS(Indian Regional Navigation Satellite System)-by INDIA
- 36. Indian Regional Navigation Satellite System Total satellites 7 First launch 1 July 2013 Last launch 28 April 2016 Orbital height 36,000 km Precision 10 m (public) 0.1 m (encrypted) Coverage -Regional (up to 1,500 km from borders)
- 38. REFERENCES GPS primer “A Student Guide”(Aerospace Corporation) www.trimble.com An Introduction – Global Positioning system S. K. Upadhyaya, G. S. Pettygrove, J.W. Oliveira, B. R. Jahn1 GPS Guide for Beginners(GARMIN Corporation)