# Navigation Elements - PowerPoint PPT Presentation

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### Navigation Elements Know the four elements of navigation. – PowerPoint PPT presentation

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1
• Know the four elements of navigation.

2
Overview
• Earths Size and Shape
• Position
• Direction
• Distance
• Time

Position
Pt A
3
Earths Size and Shape
• For most navigational purposes, the Earth is
assumed to be a perfect sphere.
• Measured at the equator, the Earth is
approximately 7,926.41 miles in diameter, and the
diameter through the poles is approximately 7,901
miles.

4
Earths Size and Shape
• Great Circles and Small Circles
• Defined as a circle on the surface of a sphere
whose center and radius are those of the sphere
itself. It is the largest circle that can be
drawn on the sphere.
• The single most important aspect of great circles
for navigators is that the arc, or piece of the
circle, is the shortest distance between two
points on a sphere.

5
Position
• Lines of reference are necessary in order to
locate specific points on the Earth.
• These lines are known as parallels of latitude
and meridians of longitude.
• The numbers representing a position in terms of
latitude and longitude are known as coordinates
of that position.

North Penn N40-14.05, W075-18.58
6
Position
• Latitude
• Parallel with the equator are lines of latitude.
Each of these parallel lines is a small circle,
and they have a definitive location.
• The equator is latitude 0o, and the poles are
located at 90o latitude. Letter designators N and
S are used to show which latitude is meant.
• Longitude
• The Greenwich Meridian is sometimes called the
prime meridian, although it is actually the zero
meridian
• Longitude is counted east and west from this
meridian through 180o

7
Direction
• Direction is the position of one point in space,
relative to another, without reference to the
distance between them.
• The points of a compass are not adequate for
modern navigation. It has been replaced, for the
most part, by a numerical system.

8
Direction
• Since determination of direction is one of the
most important parts of the navigators work, the
various terms involved should be clearly
understood.
• Course
• Track

9
Direction
10
Direction
• Now back to our navigational maps
• Lets say you are trying to get from Point A to
Point B

11
Direction
• A line that makes the same angle with each
meridian is called a rhumb line.
• Flying this sort of path results in a greater
distance traveled, but it is easier to steer.
• Between two points on the Earth, the great circle
is shorter than the rhumb line, but the
difference is negligible for short distances
(except in high latitudes).

Rhumb Line Great Circle Line
12
Direction
13
Distance
• Measured by the length of a line joining two
points. In navigation, the most common unit of
measuring distance is the nautical mile.
• The nautical mile is about 6,076 feet.
• Statute mile is 5,280 feet
• Speed If the measure of distance is nautical
miles, it is customary to speak in terms of
knots.

14
Time
• The Earth makes a complete rotation of 360o
during a 24 hour day.
• Greenwich Mean Time
• Greenwich Mean Time (GMT) is the time of day at
any given moment at Greenwich, England.
• Zulu Time
• Time zones are derived as /- from Zulu Time

15
Phonetic Alphabet and Morse Code
16