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Navigation
TWO SAD JOKES
• Who leaves the table after everyone’s
eaten?
– A cannibal.
• Why is the banana the most popular fruit?
– Because it has appeal.
How do we know where we’re at?
X
You are here. Huh?
Before GPS…. 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.
So, a set of coordinates is used that
is similar to latitude and longitude on
the Earth.
The system of latitude and longitude
was first suggested by Hipparchus, a
Greek astronomer in the 2nd C. B.C.
• 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.
More accurate: Longitude & Latitude
Longitude:
Angular distance on the
earth's surface,
measured east or
west from the prime
meridian at
Greenwich, England.
• Lines of longitude are
blue (east) and red
(west) in the drawing.
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.
• Lines of latitude are blue
(north) and red (south) in
the drawing.
Tools of the trade…
• Sexton: 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.
Sexton
• a device that
measures the angle
between two objects.
It uses the position of
stars to find it’s
latitude, longitude.
Compass
Loran C
• 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/m
od3fl5.swf