Global Positioning System

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 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

Navigation 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? 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. 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? 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 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 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 Constellation

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 Satellite

Ground 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 Segments

Websites ami/documents/gpstutorial.htmhttp://web.haystack.mit.edu/pcr/where ami/documents/gpstutorial.htm /3d/JTrack3D.html /3d/JTrack3D.html ami/documents/gpstutorial.htmhttp://web.haystack.mit.edu/pcr/where ami/documents/gpstutorial.htm /3d/JTrack3D.html /3d/JTrack3D.html

Interest 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?