Global Positioning
System
Global Positioning
System
What is GPS?What is GPS?
• A worldwide radio-navigation system– constellation of 24 satellites– with 5 ground stations
• GPS uses these “man-made stars” (statellites) as:– reference points for locations on earth– to calculate positions – accurate to a matter of meters
• A worldwide radio-navigation system– constellation of 24 satellites– with 5 ground stations
• GPS uses these “man-made stars” (statellites) as:– reference points for locations on earth– to calculate positions – accurate to a matter of meters
Common Man’s UtilityCommon Man’s Utility
• GPS receivers:– miniaturized with a few integrated circuits– thus becoming very economical
• Making this technology accessible – to all
• GPS is in:– cars, boats, planes, laptops, cell phones– construction equipment – movie making gear, farm machinery
• GPS receivers:– miniaturized with a few integrated circuits– thus becoming very economical
• Making this technology accessible – to all
• GPS is in:– cars, boats, planes, laptops, cell phones– construction equipment – movie making gear, farm machinery
NavigationNavigation• Mankind has always needed a way to:
– calculate where he is on the earth– calculate where he is going
• Old ways included – “dead reckoning”, landmarks, – observing the sun, moon, and stars
• Who wants to be lost:– at sea, in the desert, in the cold or heat, – in a war zone, – or just out hiking?
• Mankind has always needed a way to:– calculate where he is on the earth– calculate where he is going
• Old ways included – “dead reckoning”, landmarks, – observing the sun, moon, and stars
• Who wants to be lost:– at sea, in the desert, in the cold or heat, – in a war zone, – or just out hiking?
Who Developed GPS?Who Developed GPS?
• U.S. Department of Defense – spent $12 billion – creating precise form of worldwide
positioning• When/why
– in the late days of the arms race – ability to take out Russia’s missile system
• Result:– profoundly affected the balance of power
• U.S. Department of Defense – spent $12 billion – creating precise form of worldwide
positioning• When/why
– in the late days of the arms race – ability to take out Russia’s missile system
• Result:– profoundly affected the balance of power
Land vs. SeaLand vs. Sea• Russia’s nuclear system was on land• U.S. nuclear arsenal largely at sea
– on submarines• For precise targeting,
– must have accurate launching coordinates– as well as precise target coordinates
• A submarine must– surface and – accurately fix its exact position– within minutes anywhere in the world
• Russia’s nuclear system was on land• U.S. nuclear arsenal largely at sea
– on submarines• For precise targeting,
– must have accurate launching coordinates– as well as precise target coordinates
• A submarine must– surface and – accurately fix its exact position– within minutes anywhere in the world
How Does GPS Work?How Does GPS Work?• The basis of GPS is “triangulation”• To triangulate:
– GPS receiver measures distance from satellites – uses the travel time of radio signals– from 3 or more satellites
• To measure travel time, GPS needs:– very accurate timing– location of/distance of satellites– corrections for delays as signal travels through
the atmosphere
• The basis of GPS is “triangulation”• To triangulate:
– GPS receiver measures distance from satellites – uses the travel time of radio signals– from 3 or more satellites
• To measure travel time, GPS needs:– very accurate timing– location of/distance of satellites– corrections for delays as signal travels through
the atmosphere
Disturbances in SignalsDisturbances in Signals
• The ionosphere – has ionized particles (+ atoms) – exert a perturbing effect on signals
• The troposphere – is full of water vapor, – variances in temperature &
atmospheric pressure– these also disturb the GPS signals
• The ionosphere – has ionized particles (+ atoms) – exert a perturbing effect on signals
• The troposphere – is full of water vapor, – variances in temperature &
atmospheric pressure– these also disturb the GPS signals
GPS Master PlanGPS Master Plan
• Launch of the 24th block II satellite– in March 1994 – completed the GPS constellation
• Four additional satellites– in reserve to be launched “on need”
• Spacing of satellites– minimum of five satellites are in view– from every point on the globe
• Launch of the 24th block II satellite– in March 1994 – completed the GPS constellation
• Four additional satellites– in reserve to be launched “on need”
• Spacing of satellites– minimum of five satellites are in view– from every point on the globe
GPS ConstellationGPS Constellation
Satellites (Example)Satellites (Example)
• Name: NAVSTAR• Manufacturer: Rockwell International• Altitude: 10,900 nautical miles• Size: 17 ft. with solar panels extended• Orbital Period: 12 hours• Orbital Plane: 55 degrees to equatorial
plane• Lifespan: 7.5 years• Current constellation: 24 Block II
production satellites
• Name: NAVSTAR• Manufacturer: Rockwell International• Altitude: 10,900 nautical miles• Size: 17 ft. with solar panels extended• Orbital Period: 12 hours• Orbital Plane: 55 degrees to equatorial
plane• Lifespan: 7.5 years• Current constellation: 24 Block II
production satellites
NAVSTAR SatelliteNAVSTAR Satellite
Ground StationsGround Stations
• Also known as the Control Segments• Checks both the:
– operational health and– exact position of satellite in space
• Transmit corrections • Five monitoring stations:
– Hawaii, Ascension Island, Diego Garcia,– Kwajalein, and Colorado Springs
• Also known as the Control Segments• Checks both the:
– operational health and– exact position of satellite in space
• Transmit corrections • Five monitoring stations:
– Hawaii, Ascension Island, Diego Garcia,– Kwajalein, and Colorado Springs
Land Control SegmentsLand Control Segments
WebsitesWebsites
• http://web.haystack.mit.edu/pcr/whereami/documents/gpstutorial.htm
• http://www.trimble.com/gps/index.html
• http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html
• http://web.haystack.mit.edu/pcr/whereami/documents/gpstutorial.htm
• http://www.trimble.com/gps/index.html
• http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html
InterestInterest
• What ways can you think of using GPS in our daily lives
• What is the future of GPS
• What careers would be related?
• What ways can you think of using GPS in our daily lives
• What is the future of GPS
• What careers would be related?