Lesson 1: Introduction to Navigation

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Lesson 1 Introduction to Navigation

• Learning objectives
• Identify the members of the piloting team and
  their functions.
• Comprehend the administrative and operational
  organization of the Navigation Department.
• Comprehend the terrestrial coordinate system
• Comprehend the location of positions on earth
  using latitude and longitude.
• Applicable reading Hobbs, pp. 3-18.

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Introduction to Navigation

• Navigation - the process of safely and
  efficiently directing the movements of a vessel
  from one place to another.
• Marine surface navigation -
• Piloting - The navigation of a vessel in
  confined waters.
• Celestial - Navigation by celestial bodies.
• Electronic - Navigation by means such as Omega,
  loran, Global Positioning System (GPS), Satellite
  Navigation, etc.
• The Piloting Team
• Navigator and Plotter -
• Navigator- responsible for the performance of the
  piloting team , reports to the C.O. on all
  matters pertaining to the safe navigation of the
  ship.
• Plotter plots information on the chart. This
  allows the navigator to move about the bridge and
  keep the big picture.
• Bearing Recorder - supervises the bearing taker
  and plotter , ensures accuracy of the plot, and
  reports all information to the navigator.
• Bearing Taker(s) - Shoot bearings to
  navigational aids using a bearing circle and gyro
  repeater. Each bearing to a navigational aid
  provides a line of position (LOP). A fix can
  be obtained by plotting three or more LOPs.

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Introduction to Navigation

• Radar Piloting Team (normally a team located in
  CIC)
• Piloting Officer - responsible for the
  performance of the radar navigation team and
  passes information to the navigator on the
  bridge.
• Plotter - plots information on the the chart.
• Radar Operator - obtains radar ranges to
  navigational aids. A fix can be obtained from
  radar ranges to 3 or more different navigational
  aids.
• CICWO - Maintains shipping traffic picture and
  advises the Piloting Officer of contacts which
  may limit the ships ability to maneuver.
• In the event of low visibility , CIC may assume
  "primary plot".
• Echo Sounder Operator-
• Obtains depth information from the fathometer.

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The Piloting Team
Lookouts will be stationed on the next level
above the bearing taker
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Navigation Department Organization

• Administrative Organization

(Overhead 1-2)
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Navigation Department Organization

• Operational Organization

Commanding Officer
OOD
Navigator
Piloting Team
(Overhead 1-3)
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Terrestrial Coordinate System

• Earth - The Earth is a spheroid, but for
  navigational purposes, it is considered a
  perfect sphere with a circumference of 21, 600 n
  m.
• On a sphere at rest, any point on the surface
  is similar to any other point so reference
  points must be designated in order to make
  measurements on the spheres surface.
• When rotation is introduced, two reference points
  are defined - the points at which the spin axis
  pierces the surface of the sphere. On the Earth,
  these points are called the north and south
  poles.
• The axis of the Earth, together with its poles,
  constitutes the basic references on which the
  terrestrial coordinate system is based.
• Great circle - The intersection of a plane
  passing through two points on the surface of
  the earth and the center of the earth.
• The resulting circle is the largest circle that
  can be drawn on the surface of the earth.
• The resulting line on the surface of the earth
  represents the shortest distance between the two
  points.

(Overhead 1-4)
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Great Circle
Meridian
Plane Great Circle
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Terrestrial Coordinate System

• Equator - The great circle formed by passing a
  plane perpendicular to the earths axis halfway
  between its poles . The equator divides the earth
  into northern and southern hemispheres and is of
  major importance because it is one of the two
  great circles from which all locations on the
  earths surface are referenced.
• Small circle - Any circle not passing through
  the center of a sphere .

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Small Circle
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Terrestrial Coordinate System

• Meridian - Any great circle formed by passing a
  plane through the center of the earth at right
  angles to the equator.
• Prime Meridian - The meridian that passes through
  the original position of the Royal Greenwich
  Observatory near London, England.
• The prime meridian constitutes the second
  reference line for the terrestrial coordinate
  system. All other meridians are referenced to
  the prime meridian it divides the earth into the
  eastern and western hemispheres.
• All meridians lie in a true north/south direction
  and are bisected by the earths axis. The half
  of a meridian extending from the north to south
  pole on the same side of the earth as an observer
  is called the upper branch. The other half, on
  the opposite side of the earth is referred to as
  the lower side.
• The upper branch of the prime meridian is
  frequently called the Greenwich meridian while
  the lower branch is called the 180th meridian.

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Terrestrial Coordinate System

• Longitude - The angular distance between the
  Greenwich meridian and the meridian of a
  particular point on the earths surface.
  Longitude is measured in degrees of arc from 0 to
  180 degrees.
• If a point lies between 0 and 180 degrees east
  the of the Greenwich meridian, it is described
  as having eastern longitude.
• If a point lies between 0 and 180 degrees west of
  the Greenwich meridian, it is described as having
  western longitude.
• Longitude is abbreviated by the Greek letter
  lambda ( ) or LO.
• Latitude - Any small circle perpendicular to the
  earths axis formed by passing a plane parallel
  to the plane of the equator.

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Longitude and Latitude
300 60nm/deg 1800nm
1-6
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Terrestrial Coordinate System

• Latitude is measured along a meridian. The
  length of one degree of latitude is the same
  everywhere on earth (60 nm).
• Longitude is measured along parallels of latitude
  , which are small circles with the exception of
  the equator. One degree of longitude will not
  equal 60 nm except when measured along equator.
  At all other locations, as the distance from the
  equator increases, the length in miles of one
  degree of longitude decreases.