Lesson 5: Visual Navigation Aids

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Lesson 5 Visual Navigation Aids

• Learning Objectives
• Comprehend the identifying characteristics and
  significance of lighted aids to navigation.
• Apply correct procedures to identify and
  determine the computed visibility of a
  navigational light.
• Identify the shapes and lights of the U.S.
  lateral system of bouyage
• Comprehend the International Association of
  Lighthouse Authorities (IALA) Maritime Buoyage
  System.
• Comprehend the use of buoys and beacons during
  piloting.
• Applicable reading Hobbs pg. 75-105.

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Humor
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Visual Navigation Aids

• Aid to Navigation (nav aid) - Any device external
  to a vessel or aircraft intended to assist a
  navigator in determining position and safe
  course, or to warn of dangers or obstructions.
• Aids to navigation must be positively identified
  to be of use
• Daytime The location, shape, color scheme,
  auxiliary features and markings of a nav aid are
  used to identify its purpose.
• Night time The light shown by the nav aid
  becomes the primary source of identification. The
  light phase characteristic (the sequence or
  pattern of light shown within one complete cycle
  of light), duration of its period (length of time
  required for the light to progress through one
  complete cycle of changes), and its color are
  all used to determine the identity of the light.

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Visual Navigation Aids

• Lighted navigation aids are classified into two
  groups major and minor lights.
• Major lights have high intensity and reliability,
  and are normally placed in lightships, light
  houses, highly automated light towers and other
  permanently installed structures. They indicate
  key navigational points along seacoasts,
  channels, and in harbor and river entrances.
  Major lights are further subdivided into
• Primary lights - Very strong, long range lights
  used for the purpose of making landfalls or
  coastal passages.
• Secondary lights - Somewhat shorter range lights
  used at harbor entrances and other locations
  where high intensity and reliability are
  required.
• Minor lights are automated lights of low to
  moderate intensity placed on fixed structures
  that serve as navigational aids within harbors,
  along channels and rivers and to mark isolated
  dangers.

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Visual Navigation Aids

• Light Phase Characteristics
• Fixed (F.) - Shines with steady, unblinking
  intensity.
• Flashing (Fl.) - Appears as a single flash at
  regular intervals the duration of the light is
  always less than the duration of darkness.
  Flashing lights will not flash more than 30 times
  per minute.
• Quick Flashing (Qk.Fl.) - Similar to a flashing
  light, but it shows more frequently to indicate a
  greater degree of cautionary significance. The
  duration of flash is less than the duration of
  darkness, and the light will flash at least 60
  times per minute.
• Interrupted Quick Flashing (I.Qk.Fl.) - A light
  that quick flashes six times, followed by a time
  of darkness, with a standard period of ten
  seconds.
• Group Flashing (Gp.Fl.) - Shows groups of two or
  more flashes at regular intervals.
• Morse (Mo.(A)) - Shows a pattern of flashes
  comprising a Morse Code character (normally the
  letter A).
• Equal Interval (E.Int.) or Isophase (Iso.) - Has
  equal durations of light and darkness.
• Occulting (Occ.) - Any light that is on longer
  than it is off.
• Group Occulting (Gp.Occ.) - An occulting light
  broken by groups of eclipses into two or more
  flashes. The pattern of the eclipses is
  indicated on a chart enclosed by parentheses
  following the basic abbreviation, i.e.
  Gp.Occ.(23), which indicates a light interrupted
  by a group of 2, then 3, eclipses.

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Visual Navigation Aids

• Composite - A light showing 2 or more distinct
  light sequences within its period. There is no
  standard abbreviation for a composite light the
  fact that it is composite is indicated on a chart
  by a set of parentheses placed after the basic
  light characteristic. For example, a light
  abbreviation of F.Gp.Fl.(23) would indicate a
  composite fixed flashing light in which the
  flashes appeared in two groups of 2, then 3,
  flashes.
• The numbers in parentheses for a flashing light
  indicate the pattern of flashes, while the
  numbers in the parentheses for an occulting light
  indicate the pattern eclipses.
• The periods of all lights except those having
  either quick flashing or interrupted quick
  flashing phase characteristics are indicated both
  on charts depicting them and in the Light Lists
  and List of Lights.
• Color of a Light - Only three colors are used on
  lighted navigation aids in the U.S. and most
  foreign waters - white, green, and red. All
  lighted navigation aids are symbolized on a chart
  either by a purple exclamation point or by a
  1/8-inch purple circle superimposed over a black
  dot or small open circle, indicating the location
  of the light. The color of the light, if other
  than white, will be indicated by the
  abbreviations R for red or G for green. The
  abbreviation W is used in the Light List and
  List of Lights to indicate a white light.

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Visual Navigation Aids
(Overhead 4-1)
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Visual Navigation Aids

• Alternating lights change color during a regular
  pattern and are used for special applications
  requiring the exercise of great caution.
  Examples are airport beacons, harbor entrance
  lights, and lighthouses.
• Sector lights warn the navigator of hazards to
  navigation when approaching the light from
  certain dangerous arcs or sectors. Sector lights
  may be separated into two or more colored arcs or
  rendered invisible in all but one or two narrow
  arcs, by permanently positioned shields built
  around the light. Any bearings given to describe
  the limits of the various sectors are given in
  degrees true as observed from a hypothetical
  vessel moving in a clockwise direction around the
  light.

(Overhead 4-2)
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Visual Navigation Aids

• Range lights are two or more lights in the same
  horizontal direction situated in such a way that
  one is sighted over another when they are sighted
  in line. They are used mainly to mark straight
  reaches of a navigable channel between hazards on
  either side.

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Visual Navigation Aids

• When operating in coastal waters, navigators need
  to know when they can expect to first see and
  then lose sight of a navigational light. Thus,
  they want to know the computed visibility - the
  maximum distance at which a light can be seen in
  the current meteorological conditions.

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Visual Navigation Aids

• Terms associated with light visibility
  computations
• Horizon distance - the distance measured along
  the line of sight from a position above the
  surface of the earth to its visible horizon. The
  higher the position, the further the horizon
  distance will be.
• Geographic range - the maximum distance at which
  a light may be seen in perfect visibility by an
  observer whose eye is at sea level. It is
  analogous to the lights horizon distance.
• Luminous range - the maximum distance at which a
  light may be seen under existing meteorological
  conditions. It depends only on the lights
  intensity, and is independent of the lights
  elevation, observers height of eye, and the
  curvature of the earth.
• Nominal range - a special case of the luminous
  range its is the maximum distance at which a
  light may be seen in clear weather
  (meteorological visibility of 10 nm). Like
  luminous range it takes no account of the
  elevation, height of eye, or earths curvature,
  and depends only on the lights intensity.

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Visual Navigation Aids
nominal range
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Visual Navigation Aids

• Charted range - the range printed on the chart
  near the light symbol.
• Computed range - the distance at which a light
  could be seen in perfect visibility, taking its
  elevation, the observers actual height of eye,
  and the curvature of the earth.
• Computed visibility - the maximum distance at
  which a light can be seen in the current
  meteorological conditions. Computed visibility
  takes into account the existing visibility
  conditions, the intensity and elevation of the
  light, the observers height of eye, and the
  curvature of the earth. NOTE computed
  visibility differs from meteorological visibility
  which is the maximum range at which the unaided
  human eye can see an unlighted object by day in
  the current meteorological conditions.

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Visual Navigation Aids

• Computing the visibility of a light(height of
  the light 100m, height of eye 50m, visibility
  5 1/2nm, nominal range 23 nm)
• First Obtain the lights intensity, its
  elevation above water, and the luminous range of
  the light from the luminous range diagram. The
  Light List or the List of Lights will contain
  this information. The Light List provides
  information on lights and buoys in the coastal
  areas and rivers of the United States while the
  List of Lights provides similar information for
  foreign waters. The first step in using the Light
  List or List of Lights is to determine the
  luminous range from the luminous range diagram
  (Appendix A / shown in Hobbs, pp. 88). The
  luminous range can be determined by entering the
  diagram at the top or bottom with the given
  nominal range. Follow the nominal range value
  vertically until the appropriate visibility curve
  is intersected, then read the corresponding
  luminous range from the left or right hand side
  of the diagram. In our example, the light has a
  nominal range of 23 nm and we currently have 5
  1/2 nm of visibility, so the corresponding
  luminous range is 13.5 nm. NOTE the nominal
  range and luminous range are identical in 10-mile
  visibility.

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Visual Navigation Aids
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Visual Navigation Aids

• Second Find the geographic range of the light
  by using the following formula
• D (geographic range in miles) 1.144
  h(elevation in feet)
• Third Determine the horizon distance for the
  observers height of eye using the same equation
  as the geographic range.
• D(horizon distance in miles) 1.144
  h(elevation in feet)
• Fourth add the geographic range and the horizon
  distance which will yield the computed range.

1.144 (10) 11.4 nm
1.144 (7.07) 8.1 nm
(Overhead 4-6)
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Visual Navigation Aids

• Final compare the computed range to the luminous
  range. The shorter range represents the computed
  visibility. The light has a has a corresponding
  luminous range of 13.5 nm and a computed range of
  19.5 nm. Therefore the computed visibility would
  be equal to the luminous range which is 13.5 nm.
  This distance can be plotted by swinging an arc
  with a radius equal to the computed visibility
  from the light of interest across the ships DR
  track. The resultant position can be used to
  calculate the time the light can be seen by using
  ships course and speed.

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Visual Navigation Aids

• Buoys and beacons warn the navigator of some
  danger, obstruction, or change in contour of the
  sea bottom, and indicate the limits of safe
  channels through shallow water.
• Systems of Buoyage
• Lateral System - The location of each buoy or
  beacon indicates the direction of the danger it
  marks relative to the course that should normally
  be followed it is best suited for well defined
  channels.
• U.S. Lateral System - right-hand channel buoys
  are painted red and have red or white lights.
  Left-hand channel buoys are black with green or
  white lights.
• Uniform Lateral System - Right-hand buoys are
  painted black and have green or white lights.
  Left-hand channel buoys are red with red or white
  lights.
• Cardinal System - The location of each buoy
  indicates the approximate true bearing of safe
  water from the danger it marks. It is best
  suited for marking offshore, rocks, shoals,
  islets and other dangers in and near the open
  sea. The Cardinal System was standardized
  worldwide and is now known as the Uniform
  Cardinal System.

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Visual Navigation Aids

• IALA (International Association of Lighthouse
  Authorities) - Until the mid-1970s, all foreign
  countries used the Uniform Lateral System to
  mark their coastal and navigable rivers, and the
  Uniform Cardinal System to mark dangers in
  offshore areas, while the United States used the
  U.S. Lateral System. In 1977, most western
  European nations began adopting the IALA Combined
  Cardinal and Lateral System. In 1982 eighty
  maritime nations, including the United States
  adopted the IALA system which was renamed the
  IALA Maritime Buoyage System. There are
  currently two forms of the IALA System in use
  (the most significant new feature of both systems
  is the use of green vice black buoys as channel
  markers)
• IALA System A- This system is prescribed for
  Europe, Africa, and Asia. Green buoys mark the
  starboard side of a channel in the A system.
  (Navy wants to enter foreign ports)
• IALA System B - This system is prescribed for
  North, Central, and South America, Korea, and the
  Philippines. Green buoys mark the port side of
  the channel in system B. This system is the
  system used in the United States. ( Navy wants
  you out of home port)

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Visual Navigation Aids

• Types of buoys Buoys can be classified by their
  construction and by their function
• Four main types of buoy construction are in use
  in the United States
• Can buoys are usually unlighted, and are built in
  the cylindrical shape of a can.
• Nun buoys are usually unlighted and are shaped
  like a truncated cone above water, resembling the
  habit of a nun.
• Lighted buoys consist of a metal float on which
  a short skeleton tower of any shape is mounted.
  The tower supports a lantern powered by electric
  batteries in the body of the buoy.
• Sound buoys are of frame-like construction with
  various shapes and are fitted with some type of
  sound-producing device such as bells, whistles,
  gongs or horns.
• Combination buoys are buoys which have a sound
  making device and are also lighted

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Visual Navigation Aids

• Buoys can also be classified according to
  function
• Channel buoys mark the sides of , centers, and
  junctions of a channels.
• Safe water marks indicate the center of a
  channel. Preferred channel marks indicate
  junctions or splits in a channel. If the
  preferred channel, when entering from seaward,
  requires that a buoy be left to port, the top
  band is green. If the preferred channel calls for
  leaving the buoy to starboard, the top band is
  red.
• In U.S. waters, buoys that mark the right side of
  the channel when returning from sea are always
  painted red and have even numbers. Buoys that
  mark the left side are green with odd numbers.
  Remember
• 1) RED RIGHT RETURNING, and
• 2) EVEN RED NUNS HAVE ODD GREEN
  CANS..
• Special buoys mark special areas, and dangers
  such as anchorages, shoal contours, prohibited
  areas, limits of fishtrap areas, and cable
  crossings.

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Visual Navigation Aids
(Overhead 4-7)
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Visual Navigation Aids

• Cardinal buoys indicate special dangers or safe
  passages, especially offshore. They are painted
  in yellow and black horizontal bands. There is a
  different cardinal mark for each of the four
  cardinal points on the compass. An important
  feature of the buoys are the two black double
  coned marks which, coupled with their color
  scheme, identify the quadrant identified with the
  mark. The buoys indicate the direction of safe
  water from the point of interest marked by the
  buoy. They are not used extensively in U.S.
  waters.

E
(Overhead 4-8)
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Visual Navigation Aids

• Beacons are aids to navigation that are rigidly
  attached to the bottom or to the shore. They
  indicate channels and mark hazards to navigation,
  especially in shallower bays, harbors, and inland
  waterways.
• If unlighted, beacons are referred to as
  daybeacons. A geometrically shaped visual
  indicators called a daymark is normally attached
  to them to indicate what type of beacon it is.
  Daymarks are normally colored and numbered in
  the same manner as buoys, with red triangular
  daymarks indicating a right-side boundary and
  green square marks a left-channel boundary. The
  basic chart symbols for daymarks are squares and
  circles
• Left-side channel daymarks are represented by
  either a green square or an open triangle and the
  letter G while right-side daymarks have a
  purple triangle.
• Safe water daymarks are represented by an open
  triangle with the color abbreviation RW for red
  and white.
• Preferred channel daymarks are represented by an
  open triangle with the color abbreviation RG
  (red uppermost) or GR (green uppermost).
• Minor lights are often mounted on beacons to
  facilitate their use at night. These lights have
  the same phase characteristics and color as
  similarly placed lighted buoys.

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Homework

• Reading
• Hobbs, pp 106-126
• Workbook, Chapter 6
• Section 1 1, 2, 4, 6, 7,8, 9
• Section 2 3,4, 5, 8, 10,11,13,15
• Section 3 2,3,4,5,7