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# Basic Terrestrial Navigation part 1

Chapter One

## Basic Terrestrial Navigation and Shape of the Earth

Part A

It is the art of finding the position of a ship at sea and conducting her safely from place to place.
Navigation is a science in that it involves the development and use of:
1.      Instruments.
2.      Methods.
3.      Tables.
4.      Almanacs.
Navigation is an art in that it involves:
1.   The proficient use of these tools.
2.   The application and interpretation of information gained from such use.

This is the art of conducting a ship in the neighborhood of dangers, such as rocks and shoals, and in narrow water.

### 1.2.3 Importance of studying coastal navigation:

to get full details about expected dangers such as :
·                Rocks and shoals.
·                Shallow water.
·                Fishing boats.
·                Wrecks.
·                Narrow waters.
it is highly recommended to safety precautions while sailing near to the coast:
1.  High accuracy in fixing the ship.
2.  Fixing the ship at short intervals of time.
3.  Safe speed.
4. Ensure that all the required charts are available and up to
date.
5. The presence of up to date books related to artificial aids
6.  The knowledge of charts, sailing directions and other

### 1.3 The true shape of the earth:

The earth is formed by rotating a circle about its diameter. Although the earth is not a perfect sphere, it may be considered so for the purposes of navigation, as the results resulting from this assumption are always negligible.
a represents major semi axis (equatorial radius) = 3444 miles
b represents minor semi axis (polar region)        = 3432 miles
Mathematical relationship to find compression C:
C = (a-b) ÷ a = (3444-3432) ÷ 3444 = 1 / 287.
As previously mentioned, the value of compression can be neglected, however the departures from the spherical shape are only considered when:
·         Constructing charts.
·         Constructing navigational books and publications.
·         Sailing for a long period north or south of the equator.

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