From the pull down menu in the online
study select from the following topics:
If you are studying for your United States Coast Guard Deck
License exam which includes this module, you should work through
these questions until you are scoring 80% or better on them.
The recommended reference material for this subject is
the 1983 reprint of the Coast Pilot and Light List.
reference material on the Light List Vols. 1 & 2 and Coast Pilot Vols.
2 & 3 used on all deck license exams.
Aids to Navigation Terms
Adrift: Afloat and
unattached in any way to the shore or seabed.
Aid to navigation:
Any device external to a vessel or aircraft specifically intended to
assist navigators in determining their position or safe course, or to
warn them of dangers or obstructions to navigation.
A rhythmic light showing light of alternating colors.
Arc of visibility:
The portion of the horizon over which a lighted aid to navigation is
visible from seaward.
beacon: A beacon-like buoyant structure, tethered directly to the
seabed and having no watch circle. Called articulated light or
articulated daybeacon, as appropriate.
The latitude and longitude position for an aid to navigation.
Beacon: A lighted
or unlighted fixed aid to navigation attached directly to the earth's
surface. (Lights and daybeacons both constitute beacons.)
horizontal direction of a line of Sight between two objects on the
surface of the earth.
Bell: A sound
signal producing bell tones by means of a hammer actuated by
electricity on fixed aids and by sea motion on buoys.
point where a channel divides when proceeding from seaward. The place
where two tributaries meet.
to Mariners: A radio broadcast designed to provide important marine
Buoy: A floating
object of defined shape and color, which is anchored at a given
position and serves as an aid to navigation.
The audible, visual, or electronic signal displayed by an aid to
navigation to assist in the identification of an aid to navigation.
Characteristic refers to lights, sound signals, RACONS, radio beacons,
action of placing a previously discontinued aid to navigation back in
group-flashing light: A group flashing light in which the flashes are
combined in successive groups of different numbers of flashes.
group-occulting light: A light similar to a group-occulting light
except that the successive groups in a period have different numbers
direction of buoyage: The general direction taken by the mariner when
approaching a harbor, river, estuary, or other waterway from seaward,
or proceeding upstream or in the direction of the main stream of flood
tide, or in the direction indicated in appropriate nautical documents
(normally following a clockwise direction around land masses).
unlighted fixed structure which is equipped with a dayboard for
daytime identifier of an aid to navigation presenting one of several
standard shapes (square, triangle, rectangle) and colors (red, green,
white, orange, yellow, or black.)
daytime identifier of an aid to navigation.
Diaphone: A sound
signal which produces sound by means of a slotted piston moved back
and forth by compressed air. A "two tone" diaphone produces two
sequential tones with the second tone of lower pitch.
A light illuminating a sector or very narrow angle and intended to
mark a direction to be followed.
remove from operation (permanently or temporarily) a previously
authorized aid to navigation.
Failure of an aid to navigation to maintain its position or function
as prescribed in the Light List.
An easily transportable buoy used to temporarily replace an aid to
navigation not watching properly.
Dolphin: A minor
aid to navigation structure consisting of a number of piles driven
into the seabed or riverbed in a circular pattern and drawn together
with wire rope.
interval of darkness between appearances of a light.
Emergency light: A
light of reduced intensity displayed by certain aids to navigation
when the main light is extinguished.
place an authorized aid to navigation in operation for the first time.
lighted aid to navigation which fails to show a light characteristic.
Fixed light: A
light showing continuously and steadily, as opposed to a rhythmic
light. (Do not confuse with "fixed" as used to differentiate from
relatively brief appearance of a light. In comparison with the longest
interval of darkness in the same character.
Flash tube: An
electronically controlled high-intensity discharge lamp with a very
brief flash duration.
Flashing light: A
light in which the total duration of light in each period is clearly
shorter than the total duration of darkness and in which the flashes
of light are all of equal duration. (Commonly used for a
single-flashing light which exhibits only single flashes which are
repeated at regular intervals.)
Floating aid to
navigation: A buoy, secured in its assigned position by a mooring.
Fog detector: An
electronic device used to automatically determine conditions of
visibility which warrant the activation of a sound signal or
additional light signals.
Fog signal: See
The greatest distance the curvature of the earth permits an object of
a given height to be seen from a particular height of eye without
regard to luminous intensity or visibility conditions.
System (GPS): A satellite-based radio navigation system providing
continuous worldwide coverage. It provides navigation, position, and
timing information to air, marine, and land users.
Gong: A wave
actuated sound signal on buoys which uses a group of saucer shaped
bells to produce different tones.
light: A flashing light in which a group of trashes, specified in
number, is regularly repeated.
light: An occulting light in which a group of eclipses, specified in
number, is regularly repeated.
Horn: A sound
signal which uses electricity or compressed air to vibrate a disc
signal or electronic aid to navigation out of service due to a
light: A quick flashing light in which the rapid alternations are
interrupted at regular intervals by eclipses of long duration.
mark: A mark erected on, or moored above or very near, an isolated
danger which has navigable water all around it.
Isophase light: A
rhythmic light in which all durations of light and darkness are equal.
(Formerly called equal interval light.)
point where a channel divides when proceeding seaward. The place where
a distributary departs from the main stream
Lateral system: A
system of aids to navigation in which characteristics of buoys and
beacons indicate the sides of the channel or route relative to a
conventional direction of buoy age (usually upstream).
Light: The signal
emitted by a lighted aid to navigation. The illuminating apparatus
used to emit the light signal. A lighted aid to navigation on a fixed
Light sector: The
arc over which a light is visible, described in degrees true, as
observed from seaward towards the light. May be used to define
distinctive color difference of two adjoining sectors, or an obscured
Lighted ice buoy
(LIB): A lighted buoy without a sound signal, and designed to
withstand the forces of shifting and flowing ice. Used to replace a
conventional buoy when that aid to navigation is endangered by ice.
lighted beacon of major importance.
Local Notice to
Mariners: A written document issued by each U.S. Coast Guard district
to disseminate important information affecting aids to navigation,
dredging, marine construction, special marine activities, and bridge
construction on the waterways within that district.
LORAN: An acronym
for LOng RAnge Navigation, is an electronic aid to navigation
consisting of shore based radio transmitters. The LORAN system enables
users equipped with a LORAN receiver to determine their position
quickly and accurately, day or night, in practically any weather.
The greatest distance a light can be expected to be seen given its
nominal range and the prevailing meteorological visibility.
Mark: A visual aid
to navigation. Often called navigation mark, includes floating marks
(buoys) and fixed marks (beacons).
visibility: The greatest distance at which a black object of suitable
dimension could be seen and recognized against the horizon sky by day,
or, in the case of night observations, could be seen and recognized if
the general illumination were raised to the normal daylight level.
Mileage number: A
number assigned to aids to navigation which gives the distance in
sailing miles along the river from a reference point to the aid to
navigation. The number is used principally in the Mississippi River
Nominal range: The
maximum distance a light can be seen in clear weather (meteorological
visibility of 10 nautical miles). Listed for all lighted aids to
navigation except range lights, directional lights, and private aids
Occulting light: A
light in which the total duration of light in each period is clearly
longer than the total duration of darkness and in which the intervals
of darkness (occultations) are all of equal duration. (Commonly used
for single occulting light which exhibits only single occultations
which are repeated at regular intervals.)
Acquisition System CODAS): Certain very large buoys in deep water for
the collection of oceanographic and meteorological information. All
ODAS buoys are yellow in color and display a yellow light.
Off shore tower:
Monitored light stations built on exposed marine sites to replace
Off station: A
floating aid to navigation not on its assigned position.
Passing light: A
low intensity light which may be mounted on the structure of another
light to enable the mariner to keep the latter in sight when passing
out of its beam during transit.
interval of time between the commencement of two identical successive
cycles of the characteristic of the light or sound signal.
Pile: A long heavy
timber driven into the seabed or riverbed to serve as a support for an
aid to navigation,
Port hand mark: A
buoy or beacon which is left to the port hand when proceeding in the
"conventional direction of buoyage".
mark: A lateral mark indicating a channel junction or bifurcation, or
a wreck, or other obstruction which, after consulting a chart, may be
passed on either side.
Primary aid to
navigation: An aid to navigation established the purpose of making
landfall and coastwise passages from headland to headland.
Quick light: A
light exhibiting very rapid regular alternations of light and
darkness, normally 60 flashes per minute, (formerly called flashing
RACON: A radar
beacon which produces a coded response or radar paint, when triggered
by a radar signal.
electronic system designed to transmit radio signals and receive
reflected images of those signals from a "target" in order to
determine the bearing and distance to the "target".
Radar reflector: A
special fixture fitted to or incorporated in the design of certain
aids to navigation to enhance their ability to reflect radar energy.
In general, these fixtures will materially improve the aid to
navigation for use by vessels with radar.
Electronic apparatus which transmit a radio signal for use in
providing a mariner a line of position.
Range: A line
formed by the extension of a line connecting two charted points.
Range lights: Two
lights associated to form range which often, but not necessarily
indicates a channel centerline. The Front Range is the lower of the
two, and nearer to the mariner using the range. The rear range light
is higher and further from the mariner.
Rebuilt: A fixed
aid to navigation previously destroyed, which has been restored as an
aid to navigation.
A white and orange aid to navigation with no lateral significance.
Used to indicate a special meaning to the mariner, such as danger,
restricted operations, or exclusion area.
extinguished aid to navigation returned to its advertised light
Replaced: An aid
to navigation previously off station, adrift, or missing, restored by
another aid to navigation of the same type and characteristics.
(temporarily): An aid to navigation previously off station, adrift, or
missing, restored by another aid to navigation of different type
Reset: A floating
aid to navigation previously off station, adrift, or missing, returned
to its assigned position (station).
Rhythmic light: A
light showing intermittently with a regular periodicity.
Sector: See light
Setting a buoy:
The act of placing a buoy on assigned position in the water.
Siren: A sound
signal which uses electricity or compressed air to actuate either a
disc or a cup shaped rotor.
Skeleton tower: A
tower, usually of steel, constructed of heavy corner members and
various horizontal and diagonal bracing members.
Sound signal: A
device which transmits sound, intended to provide information to
mariners during periods of restricted visibility and foul weather.
mark: A buoy or beacon which is left to the starboard hand when
proceeding in the conventional direction of buoyage.
Topmark: One or
more relatively small objects of characteristic shape and color placed
on an aid to identify its purpose.
Scheme: Shipping corridors marked by buoys which separate incoming
from outgoing vessels. Improperly called SEA LANES.
An aid to navigation on its assigned position exhibiting the
advertised characteristics in all respects.
Whistle: A wave
actuated sound signal on buoys which produces sound by emitting
compressed air through a circumferential slot into a cylindrical bell
Winter marker: An
unlighted buoy without sound signal, used to replace a conventional
buoy when that aid to navigation is endangered by ice.
Winter light: A
light which is maintained during those winter months when the regular
light is extinguished. It is of lower candlepower than the regular
light but usually of the same characteristic.
discontinuance of a floating aid to navigation during severe ice
conditions or for the winter season.
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