Nav 1b Session 1

8/12/2019 Nav 1b Session 1

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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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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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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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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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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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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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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.

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Nav 1b Session 1