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?