GPS Global Positioning Systems
Published on LEARNZ (http://learnz.org.nz)
Listen: Listen to this page [1]
Listen to this page [2]
Global Positioning Systems or GPS are used to find the exact location of things. GPS
uses the time it takes for signals from four satellites to reach a receiver to calculate
an exact location.
Global Positioning Systems or GPS are used to find the exact location of things.
Who has heard of GPS?
GPS Stands for Global Positioning System and they are now used throughout the
world. A GPS unit is actually a receiver that collects signals from satellites.
Global Positioning System satellites transmit signals to GPS receivers on the ground.
Receivers require a clear view of the sky, so they are used only outdoors and do not
perform well in forests or near tall buildings.
Each GPS satellite has an atomic clock and sends a signal stating its location and
the exact time. All GPS satellites transmit at the same instant. The signals move at
the speed of light and arrive at a GPS receiver at slightly different times because
some satellites are further away than others. The distance to the GPS satellites can
be calculated by estimating the amount of time it takes for their signals to reach the
receiver. When the receiver estimates the distance to at least four GPS satellites, it
can calculate its position in latitude, longitude and height.
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GPS Global Positioning Systems
Published on LEARNZ (http://learnz.org.nz)
How GPS Works
Imagine you are somewhere in Canterbury and you are totally lost. You have
absolutely no clue where you are. You find a friendly local and ask, "Where am I?"
he says, "You are 1.4km from Christchurch’s Cathedral Square”.
That is good hard evidence but it means you could be anywhere on a 9km circle
around Cathedral Square.
You ask someone else where you are and she says “you are 5.3km from Darfield”.
Now you're getting somewhere. If you combine this information with the Cathedral
Square information, you have two circles that intersect. You now know that you
must be at one of these two intersection points, if you are 1.4km from Cathedral
Square and 5.3km from Darfield.
A third person tells you that you are 3.2km from Rangiora.
You can now eliminate one of the possibilities, because the third circle will only
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GPS Global Positioning Systems
Published on LEARNZ (http://learnz.org.nz)
intersect with one of these points. You now know exactly where you are:
Christchurch International Airport.
Each of the three circles represents the signals received from GPS satellites. The
main difference is that rather than measuring to three known locations on the
surface of the Earth, you are measuring to the known location of three GPS
satellites.
A fourth signal is used to synchronize the low accuracy clock in the GPS receiver
with the high accuracy atomic clocks in the satellites.
To get the best accuracy, surveyors use two GPS receivers to measure the distance
between two points. One of the GPS receivers is set up on a point with a known
position. This allows the surveyor to calculate the position of the second point.
Uses of GPS
GPS has many uses, for example;
Clock synchronization: The GPS time signals use highly accurate atomic
clocks. This technology can be used for things like automatic updates of
daylight saving times on cell phones.
Disaster relief and emergency services: Depend upon GPS for location.
Tracking a vehicle, person, pet or aircraft: Receivers provide continuous
tracking and can provide an alert if the receiver leaves a set area. Pets can
be chipped so they can be found if they become lost.
Navigation: eg Navman. The device uses voice activation to describe a
preferred route based on the position of the receiver, the position of the
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GPS Global Positioning Systems
Published on LEARNZ (http://learnz.org.nz)
destination and a street map.
There are many other uses for GPS: can you think of more examples?
Who has heard of GPS?
GPS Stands for Global Positioning System. GPS are now used all over the world. A
GPS unit is a receiver that picks up signals from satellites.
Global Positioning System satellites send (transmit) signals to GPS receivers on the
ground. Receivers need a clear view of the sky, so they are only used outdoors and
do not work well in forests or near tall buildings.
The satellites transmit the exact time the signals are sent. By taking the time the
signal was transmitted from the time it was received, the GPS can tell how far it is
from each satellite. The GPS receiver also knows the exact position in the sky of the
satellites, at the moment they sent their signals.
Watch this Youtube video [3] to find out more about how GPS works.
Uses of GPS
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GPS Global Positioning Systems
Published on LEARNZ (http://learnz.org.nz)
GPS has many uses, for example;
Setting time - auto updating cell phone times when daylight saving begins
and ends
Emergency services need GPS to find places
Tracking a vehicle, aircraft, person or a pet which has been chipped
Bus stops: to show how long the bus will take to arrive at a bus stop
Navigation
Personal Locator Beacons (PLBs): used to tell search and rescue experts
where someone is
Recreation: eg tramping, climbing, diving, sailing
Surveying: Surveyors use GPS locations to make maps and work out
property boundaries
Tectonics: using GPS the movement of faults during earthquakes can be
measured.
Can you think of any other uses for GPS?
Māori keywords:
pūnaha kimi
Global Positioning
taunga
System
ao whānau
worldwide, global
āmiorangi
satellite
karaka
clock
whakatere
navigation
Audio Maori keywords:
pūnaha kimi taunga - Global Positioning System [4]
ao whānui - worldwide, global [5]
āmiorangi - satellite [6]
karaka - clock [7]
whakatere - navigation [8]
How do you think GPS has changed the way you do things?
How do you think GPS has changed the way you do things?
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GPS Global Positioning Systems
Published on LEARNZ (http://learnz.org.nz)
[9]
This is an artist's impression of a GPS satellite, used to transmit location and
time signals used to calculate a position. Image: NASA.
[10]
GPS devices are useful for activities such as tramping and climbing where it
is important to know where you are. Image: LINZ.
[11]
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GPS Global Positioning Systems
Published on LEARNZ (http://learnz.org.nz)
Nic Donnelly from LINZ shows the GPS equipment used for finding exact
locations during surveying work. Image: LEARNZ.
[12]
Car navigation systems use GPS to give directions. What are the advantages
and disadvantages of using a Car navigation system? Image: LINZ
Source URL: http://learnz.org.nz/location162/gps-global-positioning-systems
Links
[1] http://learnz.org.nz/sites/learnz.org.nz/files/gps.mp3?uuid=594400a964323
[2] http://learnz.org.nz/sites/learnz.org.nz/files/gps-easy.mp3?uuid=594400a963db9
[3] https://www.youtube.com/watch?v=0n0T992ccik
[4] http://learnz.org.nz/sites/learnz.org.nz/files/punaha-kimi-taunga_0.mp3?uuid=59
4400a964489
[5] http://learnz.org.nz/sites/learnz.org.nz/files/ao-whanui_0.mp3?uuid=594400a964
59d
[6]
http://learnz.org.nz/sites/learnz.org.nz/files/amiorangi_0.mp3?uuid=594400a9646a9
[7] http://learnz.org.nz/sites/learnz.org.nz/files/karaka_0.mp3?uuid=594400a9647b1
[8] http://learnz.org.nz/sites/learnz.org.nz/files/whakatere_2.mp3?uuid=594400a964
8b6
[9] http://learnz.org.nz/sites/learnz.org.nz/files/GPS_Satellite_NASA_art-iif_0.jpg
[10] http://learnz.org.nz/sites/learnz.org.nz/files/b-lc162-01-gps.jpg
[11] http://learnz.org.nz/sites/learnz.org.nz/files/b-lc162-02-gps.jpg
[12] http://learnz.org.nz/sites/learnz.org.nz/files/b-lc162-03-gps.jpg
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