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What is GPS?

What is GPS?. GPS is a global navigation satellite system developed by the U.S. Department of Defense, managed by the U.S. Air Force. Free for anyone to use . Provides geographic locations at any time , anywhere . The Global Positioning System Constellation.

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What is GPS?

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  1. What is GPS?

  2. GPS is a global navigation satellite • system developed by the U.S. • Department of Defense, managed by • the U.S. Air Force. Free for anyone to • use. • Provides geographic locations at any time, anywhere. The Global Positioning System Constellation

  3. WGS 1984 Geographic Coordinate System Notation Degrees, Minutes, Seconds (DMS)and Decimal Degrees (DD) N 90° 0’ 0” 90.0 N 45° 0’ 0” 45.0 0° 0’ 0” 0.0 -180.0 180.0 -90.0 90.0 0.0 S 45° 0’ 0” -45.0 W 180° 0’ 0” E 180° 0’ 0” W 90° 0’ 0” E 90° 0’ 0” 0° 0’ 0” S 90° 0’ 0” -90.0

  4. GPS is a global navigation satellite • system developed by the U.S. • Department of Defense, managed by • the U.S. Air Force. Free for anyone to • use. • Provides geographic locations at any time, anywhere. • 24 - 32 earth orbiting satellites The Global Positioning System Constellation

  5. A GPS satellite Solar panels – power Atomic clock – precisely records time in UTC Radio transmitter – broadcastsa continuous signal containing the time, and ephemeris (identification and positional information)

  6. San Diego Aerospace Museum GPS satellite on display

  7. GPS is a global navigation satellite • system developed by the U.S. • Department of Defense, managed by • the U.S. Air Force. Free for anyone to • use. • Provides geographic locations at any time, anywhere. • 24 - 32 earth orbiting satellites • GPS receivers • Contain a clock, computer, radio wave receiver. • Dime sized to dinner plate sized • Receive signals from GPS satellites • Computes distance to satellite by comparing time: signal sent vs. received. • Receiving four satellite signals allows a position calculation using trilateration The Global Positioning System Constellation

  8. Trilateration – location determination through the measurement of distances. If the distance to 3 satellites is known, where these 3 spheres intersect can be calculated.Trilateration is the method used by a GPS receiver to determine one’s position on earth.Watch the explanation by a NASA scientist: • http://www.youtube.com/watch?v=3zRlbboMvb0

  9. GPS uses – Navigation Penn State University Geospatial Revolution Videos, Episode 1 (minutes 2:00 – 2:45) http://geospatialrevolution.psu.edu/episode1/complete

  10. GPS uses – Navigation (land, air, water)

  11. GPS uses - Commercial Precision agriculture Fleet management

  12. GPS uses: Military Weapon targeting and guidance Troop deployment and navigation

  13. Mission Planning to aid accuracy

  14. GPS devices – Survey, mapping, recreational • Survey grade – Very sophisticated receivers, able to receive many signals. Centimeter accuracy possible. Cost: several thousand $$. • Mapping grade – ~1 meter accuracy, possible. • Cost: $700 and up. • Recreational – User friendly, 10 meter accuracy. Cost: $100 and up.

  15. GPS Summary • 24 - 32 satellites in orbit at 20,200 km • Continuous 24-hour, worldwide coverage • Position and time data transmitted from satellites through coded radio waves. • Accuracy is depends on the sophistication of the receiver, number of signals received, and ranges from 10 meter to centimeter accuracy. • Satellites controlled by U.S. Dept. of Defense (clock adjustments, activation, signal scrambling) • WGS 1984 coordinate system used • Wide range of applications For a more involved presentation on GPS, go here

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