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?