ATONS -

With boating season upon us - let's all take a moment to review aids to navigation -

“The waters of the United States and its territories are marked to assist navigation by the U.S. Aids to Navigation System. This system employs a simple arrangement of color, shapes, numbers, and light characteristics to mark navigable channels, waterways, and obstructions adjacent to these.

Aids to Navigation can provide a boater with the same type of information that (car) drivers get from street signs, stop signs, road barriers, detours, and traffic lights. These aids may be anything from lighthouses to minor lights, day beacons, range lights, and sound signals, to lighted or unlighted buoys. Each has a purpose and helps in determining location, getting from one place to another or staying out of danger. The goal of the U.S. Aids to Navigation System is to promote safe navigation on the waterway.

The U.S. Aids to Navigation System is intended for use with Nautical Charts. Charts are one of the most important tools used by boaters for planning trips and safely navigating waterways. Charts show the nature and shape of the coast, buoys, and beacons, depth of water, land features, directional information, marine hazards, and other pertinent information.

The primary components of the U.S. Aids to Navigation System are beacons and buoys.

Beacons are aids to navigation structures that are permanently fixed to the earth’s surface. The range from lighthouses to small, single-pile structures and may be located on land or in the water. Lighted beacons are called lights; unlighted beacons are called day-beacons. Beacons exhibit a day-mark to make them readily visible and easily identifiable against background conditions. Generally, the day-mark conveys to the boater, during daylight hours, the same significance as does the aid’s light or reflector at night.

Buoys are floating aids that come in many shapes and sizes. They are moored to the seabed by concrete sinkers with chain or synthetic rope moorings of various lengths connected to the buoy’s body. They are intended to convey information to the boater by their color and shape, by the characteristics of visible or audible signal, or a combination of two or more such features” (USCG US Aids to Navigation System, 1/2001).

Need To Know

The United States utilizes the IALA (International Association of Lighthouse Authorities) Region B system running in a clockwise direction around the United States. This means south along the Atlantic (east) coast, west across the Gulf (coast) of Mexico, north on the Mississippi River (Western Rivers), and north along the Pacific (west) coast. This is known as arbitrary assumption.
A lateral aid’s meaning or significance is denoted by its color and shape.
IALA Region B means keeping the red buoys to starboard when returning from sea. Red and Green navigation aids convey lateral significance. Red Right Returning

Returning from sea…………….and returning to sea
Red aids are marked with even numbers and green aids with odd numbers. Both red and green aids grow in numerical value when viewed returning from sea (i.e., red aids 2, 4, 6, 8…etc., green aids 1, 3, 5, 7…etc.)


“Red Right Returning” (Red “even” numbered marks "Red Headed Nuns Get Even"). Unlighted RED buoys are called “NUNS” - unlighted GREEN buoys are called “CANS”


Day-beacons are planted in the dirt. Red triangle shaped marks equal the 3-R’s or “Red Right Returning”.

Preferred channel aids with both red and green horizontal color bands have lateral significance. They indicate the presence and direction of a primary channel by observing the aid’s top most color band as you would with either an all red or all green aid. The lower color band indicates the presence of a secondary channel.

Red or green aids are often fitted with a quick flashing light to indicate a bend or turn in a channel or fairway.

Yellow aids and buoys indicate a special situation and never convey lateral significance. They (yellow aids) indicate the presence of a VTS, the ICW, fish traps, etc. Yellow marks indicate a special situation

Red and White aids are called safe water buoys and have no lateral significance. These sometimes indicate the start-end of something, such as a buoyed channel and can be passed on either side. Sea buoys - Always Morse code (A)

Red and Black buoys indicate an isolated danger immediately below or adjacent to the aid and have no lateral significance. Always approach with due caution and attention. Black Balls of Death

Diamond shaped, checkered aids convey no lateral significance they convey information regarding location.

White aids with an orange boarder with diamond, square, or circle in shapes, have no lateral significance. These convey important information such as shallow water, reduced speed zones, or other regulatory information.

Range markers are used in pairs to indicate the center or safe water of a fairway or channel when vertically aligned.
Light Color - Red, green, yellow, and or white. If the light color is not designated on the chart, the color is white. See Light List.
Light Phase Characteristics – Light sequences or pattern of light shown within one complete cycle of the light. See Light List.
Light Period – The length of time required for the light to progress through one complete cycle of changes. See Light List.
Buoys - Buoys can be lighted or unlighted and are attached to a sinker which keeps it in its charted or reported position. A buoy’s color and shape are significant. Charts will show a buoy with its color, shape and light characteristic. Use the Notice to Mariners to update charts on a regular basis….a chart correction card shows the correction dates per chart.
Lighthouses - These are major structures with distinctive color and light schemes (or sequences). Many lighthouses also have sound signals - very useful in thick fog. You will find the necessary information (sound, light color and characteristic, name, height and nominal range - the distance at which the light is well visible in clear weather. It is very required to have the Coast Guard Light List in your possession - it contains a lot of useful information.
Daybeacons - These are structures similar to beacons, except they are unlighted and are usually single-pile.
Minor Lights and Beacons - These are much smaller than lighthouses, but also give light signals. They are single- or multi-pile structures, although sometimes can be also skeleton or masonry towers. They have dayboards which are plywood boards with significant shapes and colors, numbers or letters, and a reflective tape around them.