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Navigation
SAD JOKE
• Dead ahead, through the pitch-black night, the
captain sees a light on a collision course with his ship.
He sends a signal: "Change your course ten degrees
east."
"Change yours ten degrees west," comes the reply.
The captain responds, "I'm a United States Navy
captain! Change your course, sir!"
"I'm a seaman second class," the next message
reads. "Change your course, sir."
The captain is furious. "I'm a battleship! I'm not
changing course!"
"I'm a lighthouse. Your call."
How do we know where we’re at?
X
You are here. Huh?
When people first started going out in
boats they tended to stay close to shore
so they could use landmarks to guide
them.
As people ventured further (the
Hawaiians 3000BC could travel over
1000km between islands) they needed to
find other landmarks so they turned to
the stars.
1. Celestial navigation
• The pattern of
stars and planets
seen from Earth
are constant in
space. The
celestial sphere.
• It is useful to be
able to precisely
specify positions
on the celestial
sphere.
Sextant
• a device that
measures the angle
between two objects.
It uses the position
of stars to find it’s
latitude, longitude.
• The North Celestial
Pole is the point on the
celestial sphere directly
above the Earth's North
Pole.
Similarly, the South
Celestial Pole is directly
above the Earth's South
Pole.
• The star Polaris, in the
constellation Ursa Minor,
is located very close to
the North Celestial Pole.
Polaris is therefore also
called the North Star.
Latitude and Longitude
Globes, maps and charts have a system of
North-South and East-West lines which
make up the Earth’s Grid. This grid is
the basis for locating points on Earth.
Imagine a piece of graph paper covering
the planet. The intersection of two lines
determines the exact location of a point.
Latitude
The distance north or
south of the earth's
equator. 0 degrees
latitude is the
equator, the "belt"
that goes around
the "waist" of the
earth. 90 degrees
north is the North
Pole and 90 degrees
south is the South
Pole.
Longitude
Longitude:
Angular distance
on the earth's
surface,
measured east or
west from the
prime meridian
at Greenwich,
England.
Prime Meridian
Equator
Tools of the trade…
• Sextant: measures the angle between celestial bodies
and the Earth to determine position.
• Compass: Point to magnetic North, so you can follow
a course by knowing our position in relation to North.
• Loran C: radio transmissions from set positions on
the surface of the Earth, that triangulate to give you a
position.
• GPS: is a worldwide radio-navigation system formed
from a constellation of 24 satellites and their ground
stations.
Compass
Loran C (LOng RAnge Navigation)
• LORAN-C was originally developed to provide radio-navigation
service for U.S. coastal waters and was later expanded to include
complete coverage of the continental U.S. as well as most of
Alaska. Twenty-four U.S. LORAN-C stations work in partnership
with Canadian and Russian stations to provide coverage in
Canadian waters and in the Bering Sea. LORAN-C provides
better than 0.25 nautical mile absolute accuracy for suitably
equipped users within the published areas.
What is Loran-C?
• Loran-C is a low frequency/long wave electronic position fixing
system using radio signals transmissions @ 100 KHz from 3 or
more transmitters, linked in a chain. It gives a latitude and
longitude readout position to marine, aero and land receivers.
The Global Positioning System (GPS)
• is a worldwide radio-navigation system formed from a constellation
of 24 satellites and their ground stations.
• GPS uses these "man-made stars" as reference points to calculate
positions accurate to a matter of meters. In fact, with advanced
forms of GPS you can make measurements to better than a
centimeter!
• In a sense it's like giving every square meter on the planet a
unique address.
• GPS receivers have been miniaturized to just a few integrated
circuits and so are becoming very economical. And that makes the
technology accessible to virtually everyone.
• These days GPS is finding its way into cars, boats, planes,
construction equipment, movie making gear, farm machinery, even
laptop computers.
Coordinates given in Longitude, Latitude
West
East
Longitude:
40 E
Latitude:
North
South
65 N
Mapping activity
• http://olc.spsd.sk.ca/DE/k9mod/Mapskill/
mod3fl5.swf
• http://www.globenav.com/
• Youtube video:
Lost at Sea- the Search for Longitude
(a NOVA program)
What happens when you are
not a good navigator!!!