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Global Positioning SystemsA HISTORY OF THE U.S.A. GPS
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?
What is GPS?
A space based radio-navigation system used to calculate location (latitude/longitude/elevation)
accurate to a matter of meters Consists of:
a constellation of satellites Originally 24, currently 30+
Along with FIVE ground control stations
Common Man’s Use
GPS available in: cars, boats, planes, laptops, cell phones construction equipment movie making gear farm machinery
GPS receivers: miniaturized with integrated circuits thus becoming very economicalMaking GPS use accessible to all
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 nuclear arms race ability to take out Russia’s missile system
Result: profoundly affected the balance of power in
USA’s favor
USA vs. Russia Space Race
Russia launched Sputnik in 1957 Who would control outerspace?
In response USA started NASA in 1958 Put man on the moon in 1969
Nuclear Arms Race USA had superior nuclear propelled submarines
Could go to great ocean depths Hard to be detected by Russian radar Carried nuclear weapons
For precise targeting, must have accurate launching coordinatesas well as precise target coordinates
How Does GPS Work?
The basis of GPS is “triangulation” To triangulate:
GPS receiver measures distance from 3 satellites uses the travel time of radio signals to measure
distance if distance is calculated from more than 3 satellites,
even more accurate To measure travel time, GPS needs:
very accurate timing (atomic clocks) location of satellites (built in) corrections for delays as signal travels through the
atmosphere
Disturbances in Signals
In the ionosphere ionized particles (+ atoms) exert a
perturbing effect on signals
In the troposphere water vapor,
variances in atmospheric temperature
Variances in atmospheric pressure
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
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
NAVSTAR Satellite
Ground Stations
Also known as the Control Segments Control Segments check both the:
operational health and exact position of satellites in space
Transmit corrections Controlled by the U.S. Air Force
Five Control Segment Stations: Hawaii, Ascension Island, Diego Garcia, Kwajalein, and Colorado Springs
Land Control Segments
Points of Interest
What ways can you think of using GPS in our daily lives?
What is the future of GPS?
What careers would be related?
Do other countries have their own GPS?
Can they use ours?
Can we access theirs?
Civilian vs. military use?