Transcript Marine Navigation and Naval Operations I

Lesson 4: Visual Aids to Navigation
Learning Objectives:
Upon completion of this lesson, the student will:
 Be familiar with the shapes and lights of the
International Association of Lighthouse
Authorities (IALA) Combined Cardinal and
Lateral System of buoyage.
 Comprehend the use of buoys and beacons
during piloting.
Learning Objectives:
Upon completion of this lesson, the student will:
 Comprehend the identifying characteristics and
significance of lighted aids to navigation and
buoys.
 Apply correct procedures to identify and
determine the computed visibility of a
navigational light.
Significance of Nav Aids

Nav Aid: Any device external to a vessel or aircraft
intended to assist in determining position and safe
course, or to warn of dangers or obstructions.
Use of Buoys/Beacons
in Piloting

The first objective upon sighting a
NAVAID is to identify it.

After PID - make use of it
– Use fixed aids to navigation and charted structures
for shooting LOP’s whenever possible
– Bearings to buoys may be used to help clarify the
navigation picture when no other objects are
available.
Systems of Buoyage

Two general systems:
– Lateral – Location of buoy or beacon
indicated direction of danger it marks
relative to the course that should normally
be followed
– Cardinal – location of buoy indicated
approximate true bearing of safe water from
the danger it marks
Lateral Systems
of Buoyage

Lateral Systems of Buoyage
– Method: indicate the direction of danger relative to the
course that should normally be followed.
– Uses:
 Indicate sides or junctions of navigable channels
 Indicate the safe side on which to pass a hazard
 Mark the approx. centerline of wide bodies of water
Lateral Systems

US Lateral System  “IALA B”
– Red buoys mark the starboard (right) side of channels

When returning from seaward
– Green buoys mark the port (left) side of channels


When returning from seaward
Uniform Lateral System  “IALA A”
– The opposite of above
International Association of Lighthouse
Authorities (IALA)
Region “B”
Region “A”
Region “B”
• Japan
• So. Korea
• Philippines
2.1-11
Buoy and Daymark Shapes

Shape Assists in Easy
Identification.

Assigned Certain Colors for Lateral
Use.

Remember : COLOR Identifies Use.
Channel Buoys
Port Channel Buoys
Stbd Channel Buoys
Safe Water Buoys
Preferred Channel Buoys
Preferred Channel Buoys
Cardinal System
of Buoyage

Uniform Cardinal System of Buoyage
– Method: Used to indicate the approximate true
bearing of safe water from the danger it
marks.
– Uses:


Mark offshore rocks, shoals, and islets.
Mark dangers in and near the open sea.
Cardinal Buoys
The North cardinal buoy is black on top and yellow on bottom.
The safe water lies to the north of this buoy.
Cardinal Buoys
The East cardinal buoy is black with a yellow band.
The safe water lies to the east of this buoy.
Cardinal Buoys
The South cardinal buoy is yellow on top and black on bottom.
The safe water lies to the south of this buoy.
Cardinal Buoys
The West cardinal buoy is yellow with a black band.
The safe water lies to the west of this buoy.
Cardinal Marks

Used in Conjunction
With Compass to Mark
Best Water.

Yellow and Black in
Color.

Two Triangles for
Topmark.
Isolated Danger Mark

On or above an isolated
danger

Red and Black color

Topmark:
2 black vertical spaced
balls

If lighted:
Flashing (2) white light.
Special Marks

Used to identify special
areas: Military
exercise, traffic
separation scheme,
etc.

Color is yellow
Special Buoys
•
Used to mark:
–
–
–
–
•
Prohibited areas
Limits of fish traps
Cable crossings
Anchorages
Color is yellow
– Usually unlighted
Buoy Positions

Position on chart is
only an approximate
position

Anchored to sea
bottom.

Can drift off station

Not to be used to
obtain a fix!
Beacons (Daymarkers)

Permanently fixed
aids

Size from
Lighthouses to
small day boards

Readily visible and
easily identified
RACON Buoys

RACON’s are used in the U.S. for the following:
– to identify aids to navigation, both seaborne (e.g. buoys) and landbased (e.g. lighthouses)
– to identify landfall or positions on inconspicuous coastlines
– to indicate navigable spans under bridges
– to identify offshore oil platforms and similar structures
Positive Identification of
Navigation Aids

PID Criteria:
– DAYTIME
– NIGHT

Location

Phase characteristic

Shape

Period

Color Scheme

Color

Auxiliary features

Special Markings
Phase Characteristics of NAVAIDS

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.
Phase Characteristics of NAVAIDS

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 Code

Occulting
Lighted Nav Aids
Phase Characteristics
Chart Symbology for Lighted
NAVAIDS

Lighted Navaids:
– Lighted navaids have purple exclamation point ! or 1/8”
purple circle over black dot.

Floating Navaids:
– Fixed Navaids in ROMAN text
– Floating Navaids in italics text

Flashing Navaids:
– Numbers indicate patterns of light flashes
– Occulting: numbers indicate the pattern of eclipses

eg. F Gp Fl (2+3) or Gp Occ (2+3)
Special Purpose Lights

Alternating Lights
– change color following a regular pattern
– airport beacons, harbor entrance lights
SECTOR LIGHTS
•Sector
limits are expressed in
degrees true as observed from a
vessel, not from the light!

Red - Marks Danger
Areas.

Green - Marks
Turning Points or
Best Water Areas.

White - Marks Good
Water.
Ranges

Used to mark the center of the
channel.

Consist of two fix dayboards some
distance apart. The aft one is always
higher than the front marker.

Color varies:
Primary International Orange and
RANGES
•Colors Various Are
Listed Above.
•Alignment Is
Shown on the Left.
Determining the Computed
Visibility of a NAVAID

Purpose: To be able to determine, in advance,
when you should expect to gain or lose sight of a
navaid during a coastal transit.

Computed visibility = The maximum distance at
which a light can be seen given the current
meteorological conditions.
NOTE: Computed visibility  Meteorological Visibility
Determining the Computed
Visibility of a NavAid

Horizon distance = the LOS from a position above the
earth’s surface to the visual horizon.

Geographic range = the maximum distance that a
light may be seen in perfect visibility by an observer’s
eye who is at sea level.

Computed range = the distance at which a light could
be seen in perfect visibility (taking into account
elevation, observer’s height of eye, and the curvature
of the earth). CR = Horizon Distance + Geographic
Distance
Determining the Computed
Visibility of a NavAid

Luminous range = the maximum distance at which a
light may be seen under under the current
meteorological conditions.

Nominal range = a special case of the luminous range.
It is the distance a light could be seen in “clear”
weather. Also called the charted range. Appox 10
nms.

Computed visibility = The maximum distance at which
a light can be seen in the current meteorological
conditions.
Determining the Computed
Visibility of a NAVAID
First: Obtain the light’s intensity, its
elevation above water, and the luminous
range of the light from the luminous
range diagram.

Second: Find the geographic range of the
light by adding together the two horizon
distances of both the light and the
observer as follows (using Table 12 on p.
94 in Hobbs):
Determining the Computed
Visibility of a NavAid

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, p. 92).

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 in 5 1/2 nm of visibility, so the
corresponding luminous range is 15 nm.
NOTE: the nominal range and luminous range
are identical in 10-mile visibility.
Visual Navigation
Aids
–Final: compare the geographic range to the
luminous range. The shorter range represents
the computed visibility. The light has a
corresponding luminous range of 15 nm and a
geographic range of 20 nm. Therefore the
computed visibility would be equal to the
luminous range which is 15 nm.
Meteorological Optical range
Table
Code #










0
1
2
3
4
5
6
7
8
9
Weather
Yards/NM
Dense Fog
Thick Fog
Moderate Fog
Light Fog
Thin Fog
Haze
Light Haze
Clear
Very Clear
Exceptionally Clear
< 50
50-200
200-500
500-1000
.5-1 NM
1-2 NM
2-5.5 NM
5.5-11 NM
11-27 NM
Over 27 NM
Visual Navigation
Aids
11.7 NM
horizon
100 ft
ht of light
* geographic range in miles
** horizon distance in miles
Visual Navigation
Aids
horizon distance
8.1 NM
horizon
50 ft ht of eye
* geographic range in miles
** horizon distance in miles
Visual Navigation
Aids
–Fourth: add the two horizon
distances together to get the
geographic range.
geographic range = 11.7 + 8.1 = 19.8 nm
horizon
luminous range = 15 nm
Questions?
LIGHT LIST

Seven Volumes

Information on Nav
Aids in the U.S. and
its territories

Published Annually
by Department of
Transportation,
U.S. Coast Guard
Review


Types of Port and Starboard Channel
buoys and markers.
What is the difference between the Light
List and the List of Lights?