FRANKLIN ACADEMY
MS. NADAL'S K-5
S.T.E.M. LAB

Global Positioning System (GPS)

STEM Lab Technology

A Global Positioning System, also known as GPS, is a system designed to help navigate on the Earth, in the air, and on water. A GPS receiver shows where it is. It may also show how fast it is moving, which direction it is going, how high it is, and maybe how fast it is going up or down. Many GPS receivers have information about places. GPSs for automobiles have travel data like road maps, hotels, restaurants, and service stations. GPSs for boats contain nautical charts of harbors, marinas, shallow water, rocks, and waterways. Other GPS receivers are made for air navigation, hiking and backpacking, bicycling, or many other activities. The majority are in smartphones.

Most GPS receivers can record where they have been, and help plan a journey. While traveling a planned journey, it predicts the time to the next destination.

How it works

A GPS unit takes radio signals from satellites in space in orbit around the Earth. There are about 30 satellites 20,200 kilometers (12,600 mi) above the Earth.

The radio signals contain very good time and position of the satellite. The GPS receiver subtracts the current time from the time the signal was sent. The difference is how long ago the signal was sent. The time difference multiplied by the speed of light is the distance to the satellite. The GPS unit uses trigonometry to calculate where it is from each satellite's position and distance. Usually there must be at least four satellites to solve the geometric equations.

The GPS system uses a minimum of 24 satellites which continuously circle around (orbit) the Earth. Each satellite orbits the Earth 2 times every day. Scientists have designed 6 different orbit paths that provide a continuous signal to all places on the surface of the Earth.

To accurately provide a 3 dimensional location on the Earth’s surface a GPS unit on Earth must receive a signal from 4 satellites.  The precise location of each of the satellites is known.

History

The system was created by the United States Department of Defense. In the beginning, it was only used by the U.S. military, but in 1983 President Ronald Reagan made an order to allow anyone to use the system.

Some GPS receivers are separate units with their own power and display. They were the majority in the 20th century. Now, more are part of something else such as mobile phones, wristwatches, and cars.

Other Systems

There are other systems that act in the same way. One was put in space by Russia, called GLONASS. Another that is not yet done is named for Galileo and built by the European Union.

CURIOUS FACTS ABOUT GPS

1. There are a total of 31 satellites, including 2 reserve satellites, out of which at least 24 GPS satellites orbiting the earth. This means that each GPS satellite orbits the earth in every 12 hours. 

2. GPS was first used by US for military purposes. Their need of a global navigation system during the cold war triggered the introduction of GPS.

3. In the beginning, GPS was called Navstar. The first Navstar satellite was launched in 1978. Out of the ten satellites launched, only nine made it to the orbit. The first fully developed GPS satellite was launched in 1989.

4. GPS was open to the public following a disaster.  In 1983, Korean Airlines Flight 007 was shot down by Soviet Union killing 269 passengers on board as the flight entered the prohibited Soviet airspace. This incident prompted President Ronald Reagan to provide public access to the United States military satellite navigation system DNSS, which is known as GPS at present.

5. GPS was first introduced in automobiles in 1996.

10. With 31 active satellites in the orbit, GPS has become a part of every gadget we use, ranging from mobiles phones to cars.

6. If you thought GPS was all about navigation, you were wrong. It can also be used to determine the accurate time. Each GPS satellites consist of atomic clocks and time signals that the GPS receiving device can use to obtain the correct time. These signals are used to set the time in our mobile phones.

7. GPS has become very popular that GPS shoes are available in the market now, mainly aimed at locating people with Alzheimer’s disease, in case they get lost.

 Global Navigation Satellite Systems:     GLONASS      GPS    GALILEO

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https://www.youtube.com/watch?v=lWcAen3PIk4

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