Navigational Elements

1
Navigational Elements

• Know the four elements of navigation.
• 1. State how the Earths size and shape affect
  navigation.
• 2. State how to determine position.
• 3. State how to determine direction.
• 4. State how to determine distance.
• 5. State how to determine time.

2
Overview

• 1. Earths Size and Shape
• 2. Position
• 3. Direction
• 4. Distance
• 5. Time

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.
• Circles on the surface of the sphere other than
  great circles are defined as small circles.

5
Earths Size and Shape

• Great Circles and Small Circles

6
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.

7
Position

• Latitude
• The equator is a great circle midway between the
  poles, and its plane is perpendicular to a line
  connecting the poles.

8
Position

• Latitude
• The location of the latitude is determined by
  figuring the angle at the center of the Earth
  between the latitude and the equator.

9
Position

• Longitude
• Indicates east-west location.
• There is no natural starting point for numbering
  longitude.
• When the English-speaking people began to make
  charts, they chose the meridian through their
  principle observatory in Greenwich, England, as
  the zero degree line.

10
Position

• Longitude
• The Greenwich Meridian is sometimes called the
  first or prime meridian, although it is actually
  the zero meridian.
• Longitude is counted east and west from this
  meridian through 180o.
• The Greenwich Meridian is the 0o longitude on one
  side of the Earth and, after crossing the poles,
  it becomes the 180th meridian.
• These designations define the Eastern and Western
  Hemispheres.

11
Position

• Finding the Place
• If a globe has the circles of latitude and
  longitude drawn upon it and if the latitude and
  longitude of a place has been determined, a given
  point can be located on the globe in its proper
  position.

12
Position

• Finding the Place
• Latitude is expressed as either north or south of
  the equator in degrees up to 90, and longitude is
  expressed as either east or west and is expressed
  in degrees up to 180.
• A degree (o) of arc may be subdivided into
  smaller units by dividing each degree into 60
  minutes () of arc.
• Each minute may be further subdivided into 60
  seconds () of arc.
• Smaller areas can be located by going beyond
  degrees and minutes and using seconds.

13
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.

14
Direction
15
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 Intended direction of travel
• Heading where the airplane if pointed
• Track The actual direction that was traveled

16
Direction?

• Course
• In Red
• Track
• Heading
• Aircraft
• Heading changes

17
Heading Track - Course

• Note the winds

18
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).

19
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.
• Equal to 1 minute of arc on a meridian, which is
  1 minute of latitude.
• To convert nautical miles to statute miles, the
  nautical mile figure can be multiplied by the
  factor 1.15.
• To convert statute miles to nautical miles,
  multiply the statute miles by 0.87.

20
Distance

• Speed is closely related to the concept of
  distance, which determines the rate of change of
  position.
• Speed is usually expressed in miles per hour,
  either statute or nautical.
• If the measure of distance is nautical miles, it
  is customary to speak in terms of knots.

21
Time

• The Earth makes a complete rotation of 360o
  during a 24 hour day.
• Zone Time
• Before the establishment of zone time in 1883,
  every city and town had its own time.
• Each time zone is 15o of longitude (1 hour of
  angular measure) in width, and the first zone
  centers on the prime meridian.
• The United States has four standard time zones
  (in the contiguous states).

22
Time

• Greenwich Mean Time
• The use of Greenwich Mean Time (GMT) avoids the
  necessity of considering time zones.
• GMT is the time of day at any given moment at
  Greenwich, England.

23
Around the world in 24 zones!

• 24 Time Zones
• A through Z
• Zulu time last
• I and O not used

24
World View

• 24 Zones

25
Summary

• 1. Earths Size and Shape
• 2. Position
• 3. Direction
• 4. Distance
• Time
• Website for further information
• http//www.americanflyers.net/aviationlibrary/pilo
  ts_handbook/chapter_14.htm