Lesson 3: ATONS

ATONS: 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
Red aids are marked with even numbers and green aids have 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.)
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. Flash characteristic is Group Composite Flash (2 + 1) or two channels pick one
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, off-shore approach points and can be passed on either side. Sea buoys
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.
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.

Light Phase Characteristic
Fixed (F)
Flashing (Fl)
Quick Flashing (Qk Fl)
Interrupted Quick Flashing (I Qk Fl)
Group Flashing (Gp Fl)
Morse “A” (Mo (A)) Equal Interval (E Int) or Isophase (Iso)
Occulting (Occ)
Group Occulting (Gp Occ)
Composite