Types Of Marks
low marking on them. Otherwise, their col-
The IALA maritime buoyage guidelines
oring and numbering follow the same system
apply to buoys and beacons that indicate the
as other U.S. waters. The special Waterway
lateral limits of navigable channels, obstruc-
markings consist of a yellow square or yellow
tions, dangers (such as wrecks) and other
triangle and indicate to which side the aid
important areas or features. This system pro-
should be passed when following the con-
vides five types of marks: lateral, safe-water,
ventional direction of buoyage. The yellow
special, isolated danger, and cardinal (which
square indicates that the aid to navigation
are no longer used in the U.S.). Each type of
should be kept on the left side; the yellow
mark is differentiated from other types by
triangle indicates that the aid should be kept
distinctive colors, shapes, and light rhythms.
on the right side.
For complete color diagrams of the various
The conventional direction of buoyage in
types of aids to navigation, see page 289.
the Intracoastal Waterway is generally south-
erly along the Atlantic coast and westerly
Range of Lights
along the Gulf coast.
The distance from which you can see a light
Bridge Markings
depends not only on your height, the object’s
height, and atmospheric clarity, but also on
Bridges across navigable waters are gener-
the strength of the beam of light. Different
ally marked with red, green and/or white
terms are used to sort these factors.
lights. Red lights mark piers and other bridge
Nominal range is the range employed on
parts. Red lights on drawbridges show when
U.S. charts. All heights for lights are above
they are in the closed position. Green lights
high water. The state of the tide should be
on drawbridges show when they are in the
taken into account with lights of small eleva-
open position. The location of these lights
ids
tion. Nominal range is the luminous range
varies according to bridge structure.
when visibility is unlimited.
Green lights are also used to mark the cen-
Luminous range is the maximum distance
terline of navigable channels through fixed ion A
at which a light can be seen as determined
bridges. If there are two or more channels
at
by the intensity of the light and the meteo-
through the bridge, the preferred channel is
rological visibility prevailing at the time; it
also marked by three white lights in a vertical
a
v
ig
takes no account of height.
line above the green light.
N
Geographic range is the maximum distance
Main channels through bridges may be
at which a beam of light can theoretically
marked by lateral red and green lights and
reach an observer, as limited only by the
dayboards. Adjacent piers are marked with
height of the light and the refraction of the
fixed yellow lights when the main channel is
ion
atmosphere. Geographic ranges assume a
are marked with lateral aids to navigation.
at
height of eye of 15 feet (about 5 meters).
Centerlines of channels through fixed
ig
Glare from background lighting reduces
bridges may be marked with a safe-water
mark and an occulting white light when
a
v
considerably the range at which lights are N
sighted. A light of 100,000 candlepower has a
lateral marks are used to mark main chan-
nominal range of about 20 miles; with minor
nels. The centerline of the navigable channel
background lighting, as from a populated
through the draw span of floating bridges
coastline, this range is reduced to about 14
may be marked with a special mark—a yel-
miles; and with major background lighting,
low diamond with yellow retro-reflective
as from a city or from harbor installations, to
panels—and may exhibit a yellow light that
about nine miles.
displays a Morse code “B” ( – · · · ).
Figure 5 on the next page shows the light
Clearance gauges may be installed that
characteristics for aids to navigation in
indicate vertical clearance. The gauges are
U.S. waters.
located on the right channel pier, or the
structure protecting the pier when facing
Intracoastal Waterway
approaching vessels.
The Intracoastal Waterway runs parallel Drawbridges equipped with radios display
to the Atlantic and Gulf coasts from Ma- a blue-and-white sign that indicates what
nasquan Inlet, New Jersey, to the Mexican VHF channels the bridge-tender monitors.
border. Aids in these waters have some yel-
841