aids to navigation
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CHAPTER 2
AIDS TO NAVIGATION
Galveston Bay
Barbour Cut Crossing Range Front Light
County Wharf Light 3
County Wharf Light 2
Barbours Cut
Morgans Point
Cedar Bayou Channel Daybeacon Z
Houston Channel Light O1
In piloting, a ship’s position isdetermined by bearings takenon objects whose locations areshown on a chart.
AIDS TO NAVIGATION
2
LIGHTHOUSE
LIGHT SHIPS
RADIO
BEACONS
FOG
SIGNALS
BUOYS
DAYBEACONS
• Color
• Pattern of flashes
• Visibility or timing
interval (period)
Light
Characteristics:
The timing interval of a light is
considered the most valuable
for identification purposes.
Symbols
describing
lights are printed
on navigation
charts.
• Fixed
• Flashing
• Occulting
Light characteristics have three
principal patterns of light flashes:
Fixed lights burn constantly.
Example ON – 5 seconds
OFF – 15 seconds
Flashing lights show a single flash at
regular intervals.
The duration of light being greater
than the duration of darkness
Occulting Lights
Always have two or more off
periods at regular intervals
Group Occulting Lights
Equal interval — Duration of light
equals that of darkness
Light characteristics
variations include:
Morse Code - Light
flashes represent
a Morse code
character (usually
the letter A)
Alternating - Rhythmic
lights show different
colors during each
sequence
Visibility of a Light
The distance, in
nautical miles, a
mariner can see
the light at night
Visibility Factors
• Intensity
• Weather
• Height of light
and observer
The distance a light
will shine in clear
weather, about the
distance a mariner
in a small boat can
usually expect to
see the light, is
printed on nautical
charts beside the
light symbol.
Charted Range
Many lighthouses and light towers
are found along the coastlines of
the United States.
A powerful light of a lighthouse
which may be of assistance to
navigators, or where very dangerous
water requires a warning beacon
of long-range visibility
Primary Light
Primary Light
Increase height of a light above sea
level
Purpose of lighthouses:
Lighthouses and light towers may
contain fog-signaling and radio-beacon
equipment.
A light tower
is located
where
conditions
make it
impossible
to build a
permanent
structure on
land.
N
175°
355°
True sector
bearings
clockwise around
the light — ―Red
sector indicates
Danger Sector‖
N
175°
355°
True sector
bearings
clockwise around
the light — ―Green
sector indicates
Turning Point or
the best water
across a shoal‖
Navigational Buoys
A distinctively shaped and marked
float, sometimes carrying a signal
or signals, anchored to mark a
channel, anchorage, navigational
hazard, etc., or to provide a mooring
place away from the shore
Buoy
They may be of various sizes and
shapes, but it is mainly coloring that
indicates their purpose.
Buoys
Buoy symbols are printed on charts,
so buoys can be used for determining
positions in piloting.
(Chart Symbol)
―9‖
GI G4 sec
Ra Ref
9
Can Buoy
CHART SYMBOL
RB
C‖N‖
Ra Ref
Types of Buoys used in the U.S.
1. Spar2. Can3. Nun4. Bell5. Whistle, or horn6. Gong7. Lighted8. Combination
Spar Buoy
Upright wooden
poles, or tubes
of steel, which
are often used
to mark
obstructions
Can Buoy
Cylindrical in
shape like an
oil drum; if
unlighted,
green left-hand
channel buoys
must be can
buoys.
Conical in shape,
if unlighted,
red right-hand
channel buoys
must be nun
buoys.
Nun Buoy
They have a framework
that supports a bell.
The motion of the sea
sounds older bell
buoys. Newer types are
operated automatically
by compressed gas or
electricity.
Bell Buoy
Similar in shape to a bell buoy, but they carry
a whistle sounded by the sea’s motion or
horns that are sounded at regular intervals by
mechanical or electrical means.
Whistle or Horn Buoy
Gong Buoy
Similar in shape to a bell buoy, they have a
series of hammered gongs, each with a
different tone, moved by the motion of the
sea.
Lighted buoys
carry batteries or
gas tanks and
have a framework
that supports a
light.
Lighted Buoy
Combination buoys have a light and sound signal combined, such as a lighted bell, gong, or whistle buoy.
Combination Buoy
Red buoys on right when returning
will keep you safe.
Preferred
channel to
port
Preferred
channel to
starboard
Preferred Channel Markers
Mark the middle of a channel
Safe-Water Buoys
SPEED
LIMIT
QUARANTINE
ANCHORAGE
DREDGING
Other
Buoys
ANCHORAGE
AREA
FISHTRAP
AREA
Other Buoys
Controlled
Area
Danger Boats
Keep Out
Information
Do Not Pass
Between
Shore and Buoy
Anchor
Buoy
Diver
Below
Port Side Returning Starboard Side
Solid Green and Solid Red Buoys
Usually found in pairs
Pass between these buoys
U.S. Lateral System (Region B) Port Side
U.S. Lateral System (Region B) Starboard
Intracoastal WaterwaySecondary ChannelPreferred Channel
For ships returning to port, buoys on the right
are red with even numbers.
Just Remember — RED – RIGHT - RETURNING!
Intracoastal WaterwaySecondary ChannelPreferred Channel
Lights On Buoys
Green lights only on green channel
buoys
Red lights only on red channel buoys
White Light Buoys
White lights are used on preferred-
channel (junction) or safe-water
(mid-channel) buoys.
Characteristics of lighted buoys:
1. A fixed light may be on either a
green or red channel buoy.
Characteristics of lighted buoys:
1. A fixed light may be on either a
green or red channel buoy.
2. A regular interval light flashing at
not more than thirty flashes per minute
may be on either a green or red buoy.
Characteristics of lighted buoys:
1. A fixed light may be on either a
green or red channel buoy.
2. A regular interval light flashing at
not more than thirty flashes per minute
may be on either a green or red buoy.
3. A light flashing at no fewer than
sixty flashes per minute may be on
either a green or red buoy at a turning
point or junction where special caution
is required.
Characteristics of lighted buoys:
4. An interrupted quick-flashing light
(repeated series of quick flashes,
separated by four-second dark
intervals) may be on a red and green
horizontally banded preferred-channel
buoy.
Characteristics of lighted buoys:
4. An interrupted quick-flashing light
(repeated series of quick flashes,
separated by four-second dark
intervals) may be on a red and green
horizontally banded preferred-channel
buoy.
5. A Morse code ―A‖ flashing light
(short and a long flash, recurring at
the rate of about eight per minute)
may be on a red and white vertically
striped safe-water buoy.
Daybeacons
Unlighted navigational beacons
used as a daymark
Daybeacons
A navigational aid distinctively
marked for visibility by day
Daymark
Daybeacon Range
Two daybeacons, located some distance
apart on a specific true bearing
A channel in which a light-draft vessel can navigate along the U.S. East Coast from Chesapeake Bay almost to the Mexican border without going into the ocean
Intracoastal Waterway
Daymark Daymark
NunCan Lighted
Buoy
Lighted
Buoy
STARBOARD SIDEPORT SIDE
Intracoastal Waterway
Chart No. 1
contains nautical
chart symbols,
abbreviations,
and terms.
AIDS TO NAVIGATION
The END
What are the characteristics of
navigational aid lights?
Q.1.
What are the characteristics of
navigational aid lights?
Q.1.
Color, pattern of flashes, and
timing interval (period)
A.1.
Which identifying factor of a
navigation light is most
important?
Q.2.
Which identifying factor of a
navigation light is most
important?
Q.2.
Timing interval A.2.
What are the three general
patterns of lights?
Q.3.
What are the three general
patterns of lights?
Q.3.
Fixed, flashing, and occulting A.3.
Name the standard colors of
lights used on aids to
navigation.
Q.4.
Name the standard colors of
lights used on aids to
navigation.
Q.4.
Red, green, and white A.4.
What is meant by the timing
interval of lights?
Q.5.
What is meant by the timing
interval of lights?
Q.5.
The time and spacing of the on-
off cycle
A.5.
What factors determine the
range of visibility of a light at
night?
Q.6.
What factors determine the
range of visibility of a light at
night?
Q.6.
Brilliance, height of the light,
height of the observer's eye,
and weather conditions
A.6.
What is the function of a
lighthouse?
Q.7.
What is the function of a
lighthouse?
Q.7.
To project its light where it can
be seen at great distances as an
aid to navigation and as a
warning of dangerous waters.
A.7.
What is the main purpose of a
lighthouse?
Q.8.
What is the main purpose of a
lighthouse?
Q.8.
To increase the height of a light
above sea level
A.8.
What are the two primary
purposes of buoys and what do
they represent?
Q.9.
What are the two primary
purposes of buoys and what do
they represent?
Q.9.
To serve as warning signs and
guideposts:
a. Can buoys for left-hand side
of channel (green)
b. Nun buoys for right-hand
side of channel (red)
A.9.
What are the two primary
purposes of buoys and what do
they represent?
Q.9.
To serve as warning signs and
guideposts:
c. Spar buoys for mid-channel
or obstructions
A.9.
A ship entering Norfolk harbor
will find what color buoy to
starboard?
Q.10.
A ship entering Norfolk harbor
will find what color buoy to
starboard?
Q.10.
Red A.10.
What system of buoyage is
used in the United States?
Q.11.
What system of buoyage is
used in the United States?
Q.11.
IALA System B A.11.
What are the various types and
shapes of buoys?
Q.12.
What are the various types and
shapes of buoys?
Q.12.
Spar, can, nun, bell, whistle,
gong, lighted, and combination
A.12.
What does a red and green
horizontally banded buoy
indicate?
Q.13.
What does a red and green
horizontally banded buoy
indicate?
Q.13.
Obstruction or junction A.13.
What do vertically red and
white striped buoys indicate?
Q.14.
What do vertically red and
white striped buoys indicate?
Q.14.
Middle of the channel A.14.
A ship leaving Boston harbor
will find what color buoy to
port?
Q.15.
A ship leaving Boston harbor
will find what color buoy to
port?
Q.15.
Red A.15.
How are buoys numbered in
the United States?
Q.16.
How are buoys numbered in
the United States?
Q.16.
Coming from seaward, green
buoys have odd numbers
starting with ―1‖; red buoys
have even numbers.
A.16.
What is the difference between
an occulting light and a
flashing light?
Q.17.
What is the difference between
an occulting light and a
flashing light?
Q.17.
Occulting is on for longer
periods than it is dark, while
flashing is on for shorter
periods than it is dark
A.17.
Briefly explain why the captain
of a ship should not rely totally
on the buoys marking a
channel.
Q.18.
Briefly explain why the captain
of a ship should not rely totally
on the buoys marking a
channel.
Q.18.
The buoy can slip its moorings
or be defective in some way
A.18.
What is a daybeacon? Q.19.
What is a daybeacon? Q.19.
An unlighted aid to navigation
made of almost any kind of
material and colored to be
easily spotted on the
landscape
A.19.
Two daybeacons on a true
bearing are called what?
Q.20.
Two daybeacons on a true
bearing are called what?
Q.20.
A range A.20.
What does the phrase "on the
range" mean?
Q.21.
What does the phrase "on the
range" mean?
Q.21.
The two daybeacons are
exactly in line as seen by a
ship’s pilot or conning officer
A.21.
How can you distinguish
between a channel buoy and a
buoy on the Intracoastal
Waterway?
Q.22.
How can you distinguish
between a channel buoy and a
buoy on the Intracoastal
Waterway?
Q.22.
Buoys on the Intracoastal
Waterway have yellow bands
painted on them
A.22.
What is the name of the chart
that shows all the nautical
symbols, abbreviations, and
terms?
Q.23.
What is the name of the chart
that shows all the nautical
symbols, abbreviations, and
terms?
Q.23.
Chart No. 1 A.23.
A. Nun
B. Priest
C. Can
D. Bottle
What types of buoys if
Unlighted, are red channel buoys?
A. Nun
B. Priest
C. Can
D. Bottle
What types of buoys are always
unlighted red channel buoys?
A. Nun
B. Can
C. Priest
D. Bottle
What types of buoys are unlighted
green channel buoys?
A. Nun
B. Can
C. Priest
D. Bottle
What types of buoys are unlighted
green channel buoys?
AIDS TO NAVIGATION
The END
FIXED
FIXED AND FLASHING
FIXED AND GROUP FLASHING
FLASHING
COMPOSITE GROUP FLASHING
QUICK FLASHING
OCCULTING
Characteristics of Lights
Various Light Lists
LIGHT LIST
DISTANCE OF VISIBILITY
LUMINOUS RANGE DIAGRAM
CHART SYMBOL
RB
N‖6‖
Ra Ref
Nun Buoy
6
A mostly inland water route, partly
natural and partly artificial,
extending 1550 mi. (2500 km) along
the Atlantic coast from Boston to
Florida Bay (Atlantic Intracoastal
Waterway) and 1116 mi. (1800 km)
along the Gulf coast from Carrabelle,
Florida, to Brownsville, Texas
Intracoastal Waterway
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