1.Global Positioning System (GPS)

2. Overview Official name of GPS is NAVigational Satellite TimingAnd Ranging Global Positioning System (NAVSTAR GPS) Global Positioning Systems (GPS) is a form of Global Navigation Satellite System (GNSS) Only completely functional one of its kind at this time First developed by the United States Department ofDefense Consists of two dozen GPS satellites in medium Earth orbit (The region of space between 2000km and 35,786 km) 3. Overview (continued) Made up of two dozen satellites working in unison areknown as a satellite constellation This constellation is currently controlled by the United States Air Force 50th Space Wing It costs about $750 million to manage and maintain the system per year Mainly used for navigation, map-making and surveying 4. Operation Overview A GPS receiver can tell its own position by using theposition data of itself, and compares that data with 3 or more GPS satellites. To get the distance to each satellite, the GPS transmits a signal to each satellite. The signal travels at a known speed. The system measures the time delay between the signaltransmission and signal reception of the GPS signal. The signals carry information about the satellites location. Determines the position of, and distance to, at least three satellites, to reduce error. The receiver computes position using trilateration. 5. Trilateration 6. GPS Functionality GPS systems are made up of 3 segments Space Segment (SS) Control Segment (CS) User Segment (US) 7. Space Segment The space segment consist of 30 actively broadcastingsatellites in the GPS constellation. GPS satellites fly in circular orbits at an altitude of 20,200 km and with a period of 12 hours. Satellites are travelling at a speed of 7000 miles an hour. They are powered by solar energy and built to last about 10 years. 8. Space Segment (Continued) The satellites continuously orient themselves to pointtheir solar panels toward the sun and their antenna toward the earth. Orbital planes are centered on the Earth Each planes has about 55 tilt relative to Earth's equator in order to cover the polar regions. They also have rocket boosters to keep them flying in the correct path. 9. Control Segment 10. Control Segment The control segment comprises of 5 stations. They measure the distances of the overhead satellites every 1.5 seconds. Here the satellite orbit, clock performance andhealth of the satellite are determined 11. Control Segment The CS consists of 3 entities: Master Control System Monitor Stations Ground Antennas 12. Master Control Station The master control station, located at Falcon Air ForceBase in Colorado Springs, Colorado, is responsible for overall management of the remote monitoring and transmission sites. 13. Monitor Stations Six monitor stations are located at Falcon Air ForceBase in Colorado, Cape Canaveral, Florida, Hawaii, Ascension Island in the Atlantic Ocean, Diego Garcia Atoll in the Indian Ocean, and Kwajalein Island in the South Pacific Ocean. Each of the monitor stations checks the exact altitude, position, speed, and overall health of the orbiting satellites. 14. Monitor Stations (continued) The control segment uses measurements collected bythe monitor stations to predict the behavior of each satellite's orbit and clock. The prediction data is up-linked, or transmitted, to the satellites for transmission back to the users. 15. Ground Antennas Ground antennas monitor and track the satellites fromhorizon to horizon. They also transmit correction information to individual satellites. 16. GPS Transportable Ground Antenna Cape Canaveral Air Force Station 17. GPS Roof Antenna 18. User Segment The user segment simply consist of us and our GPSreceiver. GPS receivers are generally composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly-stable clock, commonly a crystal oscillator). They can also include a display for showing location . As of recent, receivers usually have between twelve and twenty channels. 19. GPS Used in Cars 20. GPS as Land Survey Equipment 21. GPS- U.S. Strategic Command 22. GPS Space Segment Video 23. Refrences US Strategic Command US Public GPS gps.gov Geoview GPS Research Wikipedia : GPS Rooftop Antenna MIT GPS Lab 24. Thanks