on Earth? A Look at GPS
on the GPS receiver to see what each button is for. Photo OM
Imagine waking up in the middle of nowhere, all alone. How would you
know where you were? On a clear night, you could look up at the stars.
If you could measure precisely what angle various stars were from you
at precise hours, you could calculate your position. That is what sailors
did for many centuries, using a special tool called a sextant.
birds that migrate at nighttime use the stars for navigation, too.
They simply migrate toward or away from the North
Navigating Made Easier
The problem with depending on the stars to set a direction or find out
where you are is that stars are only visible at night, and only when
clouds don't cover them. That's why the Global Positioning
System (GPS) was started. Instead of stars,
this system uses satellites—"human-made stars." GPS
is a worldwide radio-navigation system based on 24 satellites and their
ground stations. Each of the satellites sends out a unique radio signal.
GPS receiver (click the photo to enlarge) works like
a radio, but it gets
signals from the satellites instead of from radio stations. As long
as a GPS receiver can get signals from at least three or four satellites,
it can calculate precisely where
on Earth it is. The calculations are based on the time it takes for signals
from the satellites to reach the receiver. GPS can be used to figure
where you are on the planet—any time of day, in any weather.
Right Along: GPS Helps!
GPS receiver can do more than calculate where it is. It can also keep
a constant record of its altitude and how fast it is moving. The
ultralight pilots rely on their GPS receivers to tell them how far
how long they must fly before they get too their stopover sites. This
lets them know if the birds can make it without tiring and needing to
land. If a crane gets tired and drops out, the pilot can radio the location
to ground trackers, who can then locate the "missing" bird
with tracking equipment.
this! Journal or Discuss
the ultralight airplanes flying with the cranes have GPS receivers,
why do you think each also has an altimeter
and a speedometer?
the GPS receiver show the plane's ground speed or air speed? Why?
receivers are on airplanes, buses, and many cars. When have you
been in a car when a GPS could be helpful?
Journey North is pleased to feature this educational
adventure made possible by the Whooping
Crane Eastern Partnership (WCEP).