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GENERAL OBJECTIVES
Student will able to describe the coordinate
system of the earth, and set out positions stated
by:
Latitude and longitude;
True bearing and distance from a given point,both in meters and in nautical miles.
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Specific Learning Outcomes
At the end of this session, you will be able to:
1. State what coordinate system use to locate places on
Earth;
2. List the main terrestrial coordinates;3. Define Latitude, Longitude, Equator, Parallels of Latitude,
Meridians and the Prime Meridian
4. Outline the salient features of Latitude, Longitude,
Equator, Parallels of Latitude, Meridians and the PrimeMeridian
5. Using a sphere (drawn on paper) draw, Latitude,
Longitude, Equator, Parallels of Latitude, Meridians and
the Prime Meridian
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THE COORDINATE SYSTEM OF THE EARTH
The first step in
converting the
information
contained in thereal-world.
.onto a piece of
paper was to
devise a system
where everything
could be uniquely
located in that
world.
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THE COORDINATE SYSTEM OF THE EARTH
Very early maps (which
usually showed small local or
regional areas) used a grid
technique which relied onsimply measuring the
distance and direction
between points of interest
and then plotting these onto
the piece of paper.
This method assumed that
the Earth was flat.
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THE COORDINATE SYSTEM OF THE EARTH
With the general agreement
that the Earth was, in fact,
round;
A different methodologyneeded to be developed.
The system that has been
developed over many
centuries is called
LATITUDEand LONGITUDE.
The location and
measurement of latitude
and longitude essentially
involves complexmathematics (especially
geometry) and a series of
international agreements,
conventions for recording
locations on the surface ofthe Earth.
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THE COORDINATE SYSTEM OF THE EARTH
LATITUDE
The first convention to be developed was latitude. This is
based on long term astronomical observations about how
the sun is perceived to move across the surface of theEarth.
These observations also developed the conventions that the
sun:
* rises in the east and sets in the west
* is in the south during a European winter and in the
north in a European summer
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THE COORDINATE SYSTEM OF THE EARTH
Latitude
It was agreed that a line
around the center of theEarth would be called
the EQUATOR.
This would be
numbered as zerodegrees (0) of latitude.
The equator is an imaginary linethat divides the earth into two
equal parts called the Northern
Hemisphere and the Southern
Hemisphere.
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THE COORDINATE SYSTEM OF THE EARTH
Latitude
From the Equator a series of
parallel lines were
recognized with the mostnorthern and southern points
being called the North Pole
and South Pole.
These would be numberedas 90 degrees North and
South respectively (90N and
90S).
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THE COORDINATE SYSTEM OF THE EARTH
Latitude
These would be
numbered as 90degrees North and
South respectively
(90N and 90S)
measured from the
center of the
sphere.
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Four significant lines of latitude were also agreed
upon. These are:
* 0 - THE EQUATOR
* 23.5N and S - The
Tropics (called
Cancer in the north
and Capricorn in the
south)
* 66.5N and S - The Polar
Circles
* 90N and S - The Poles
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Because lines of latitude are likeslices through the Earth they have
different lengths. For example:
* the Equator is 40,075 K long
* the Antarctic Circle is 17,662 K
long
* the South Pole is 0 K long
For obvious reasons, lines oflatitude are called parallels.
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Salient Features of Parallels of Latitude
1. Lines of latitude are imaginary lines drawn around the
Earth from east to west ;
2. Each line runs parallel to the others and is measured
in degrees.3. These lines are called parallels of latitude because
they run parallel to each other.
4. The most important line of latitude is the Equator.
5. The Equator divides the Earth into two halves: the
Northern Hemisphere and the Southern Hemisphere.6. There are 90 degrees parallels of latitude to the north
and 90 degrees to south of the equator.
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Defining longitude was
much more difficult, as it is
could not be based on
observations of movementof the sun.
The convention eventually
agreed upon was to have a
series of radiating lineswhich run vertically around
the Earth.
LONGITUDE
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They connected at both endsie atthe North Pole and the South Pole.
As a result of this, a series of slices
much like slices of an orange are
created. These are pointed at theirends and broadest in the middle.
It was agreed that a primary line of
longitude should be identified and
that this should be zero degrees(0) of longitude.
LONGITUDE
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LONGITUDEFor a considerable period of time the issue of which
line of longitude was to be the primary line could not
be agreed.
For obvious religious reasons, early European maps
often used Jerusalem as the primary line of longitude.
Because of its status as a center of learning other
early map makers, such as Ptolemy, had used
Alexandria in Egypt.
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LONGITUDEMore commonly though, for
patriotic reasons, many
countries chose one of their
cities.A few European examples are
Copenhagen, Madrid, Paris
and Saint Petersburg; while in
the United States of AmericaWashington and Philadelphia
had been chosen.
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LONGITUDEEventually, in October
1884, at the International
Meridian Conference, it
was agreed that the line oflongitude that runs through
the Royal Observatory,
Greenwich in United
Kingdom, was to be
adopted as the standard
primary line of longitude.
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Prime Meridian: (Also called Greenwich Meridian) A line of
constant longitude (=0o) running from the North Pole throughGreenwich, England, to the South Pole.
The Prime Meridian
passes through the oldRoyal Astronomical
Observatory (now a
museum) at Greenwich,
England which is veryclose to London.
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LONGITUDERadiating to the east and to the
west would be 180 of longitude.
These would meet at the
opposite side of the Earth andform a joint 180 line of
longitude (with 180E and
180W being the same line).
Lines of longitude are called
MERIDIANS.
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Salient Features of Meridians of Longitude
1. LONGITUDE: Lines of longitude are imaginary lineswhich run in a north-south direction from the North Pole to
the South Pole.
2. The lines are also called meridians of longitude and they
are also measured in degrees.3. The most important line of longitude is the Greenwich, of
Prime Meridian.
4. This line runs through the Greenwich Observatory in
London.
5. All the other lines of longitude are given a number
between 0 degrees and 180 degrees East or West.
6. The Earth is divided into two halves along the Greenwich
Meridian: the Western Hemisphere and the Eastern
Hemisphere.
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LATITUDE & LONGITUDEAdd the Two Together
Combine latitude and
longitude together and we
have a system to recordthe location of any feature
on the surface of the
Earth uniquely.
THIS CALLED THE
TERRESTRIAL COORDINATE
SYSTEM
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THE TERRESTRIAL COORDINATE SYSTEM
The coordinate system
that we use to locate
places on Earth is the
terrestrial system.
The coordinates in the
terrestrial system are
latitude and longitude.
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Latitude is measured in degrees North or South of theequator.
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Longitude is
measured in
degrees East or
West of the Prime
Meridian or
Greenwich
Meridian (they are
the same thing)
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Special points and lines in the terrestrial system are the:
- Equator (0' latitude)Equator: A line around the Earth 90o from the North Pole
or the South Pole; the line of latitude = 0o.
- North and South Poles (90' latitude N or S)
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Latitude: Acoordinate
measured north (N)
or south (S) of the
equator on theEarth, in degrees.
The North Pole is
90oN. Latitudes S
are sometimes (butnot usually) given
as negative
numbers.
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Longitude:
A coordinate
measured east (E) or
west (W) of the PrimeMeridian.
Longitudes W are
sometimes (but notusually) given as
negative numbers.