Aids to Navigation - (AtoN’s/NavAids)

An Introduction to AtoN’s/NavAids

Aids to Navigation (AtoN’s) or Navigational Aids (NavAids) are any sort of navigation mark, signal, or guidance, (fixed or floating) which aids in marine navigation and the safe passage of a vessel when in confined or dangerous waters.

They are specifically intended to assist the navigator in determining their position, a safe course to travel, or to warn them of dangers or obstructions. They include visible, audible and electronic aids established by governments and private authorities for these purposes.

The most often thought of NavAids are buoys, but also included in this list are lighthouses, lightships, beacons, RACONs, fog signals, radio direction beacons, and range lights.

Regardless of the type, they are all often referred to as "AtoN’s," "Navigation Marks," "NavAids," or simply "Marks."

Some Background

If you are a serious worldwide cruiser, then you are probably aware that the buoyage system is not the same everywhere in the world. In fact at the end of 1970's, there were more than 30 different buoyage systems in use. It became apparent that a universal system needed to be developed to provide a solution to this confusing and oft time dangerous problem.

In 1971, (2) maritime accidents occurred in the Straits of Dover; the German Flagged "Brandenburg" and the Peruvian Flagged "Niki." These (2) accidents, resulted in the loss of 51 lives, occurred less than 2 months apart, and were caused by striking the same well marked sunken wreck. This became the impetus to bring about worldwide changes to the confusing buoyage systems of the time.

"Enter the IALA"

So Who or What is the IALA?

The "International Association of Marine Aids and Lighthouse Authorities" (IALA), originally the "International Association of Lighthouse Authorities," was established in 1957 to provide nautical expertise and advice on Aids to Navigation.

Maritime experts from around the world were brought together to develop recommendations on new technologies and improved practices to aid in safety at sea. There most notable accomplishment being the development of the "IALA Buoyage System" which was officially implemented in 1982.

The IALA Buoyage System, for the most part, ended years of confusion for most mariners and increased safe navigation for all mariners. Needless to say, the system is not perfect. Due to the "Mine is Bigger than Yours" syndrome that afflicts many countries, the IALA finally had to settle on a system that divided the planet into (2) distinct regions. But having (2) systems, "Region A" and "Region B,"” with minimal differences is a whole lot better than (30+) different systems we had previously.

"Region A" and "Region B"”

To make use of the IALA Buoyage System, the mariner has to know which region he is in. The chart below shows the delineation of Regions A and B.

IALA Regions

You may often see references to IALA-A or IALA-B, this is simply shorthand for Regions A & B.

IALA-A includes parts of the Atlantic Ocean, Africa, Europe, Asia, Middle East, Australia, Indian Ocean, and parts of the Pacific Ocean.

IALA-B is the Americas; North, Central, and South. From Ellesmere Island in the Canadian Artic south to Tierra del Fuego, near the Straits of Magellan, in South America. It also includes parts of the Atlantic Ocean, Philippines, Japan, Korea, and parts of the Pacific Ocean.

The Differences

The differences between the (2) IALA regions are few. In fact the only noteworthy difference is found in the "Lateral Buoy Marks." In short, IALA-A and IALA-B differ as to what "color" - marks which side of the channel when returning from sea.

IALA Regions A & B

In the waters of Region A, "Green Marks" are used to mark the right side of the channel when entering from sea while Region B retains "Red Right Returning."

Common Types of NavAids


Generally a tower, building, or other structure that is built onshore or attached to the seabed. It contains a beacon light designed to warn or guide vessels at sea or on inland waterways.

Lighthouses typically mark dangerous coastlines, off lying hazardous shoals, reefs, rocks, as well as safe entries to harbors. Once widely used, the number of lighthouses has declined due to maintenance costs and the economics of operation.

Buoys and Beacons


Are floating objects anchored to the sea bottom that are distinctively shaped, marked, and colored; designed to warn or guide vessels at sea, on their approaches to harbors and ports, and on inland waterways.

In addition to their shapes, colors, and markings, they often carry lights, sound devices, or electronic signals to further aid in their identification and purpose. Buoys are typically used to mark anchorages, caution areas, navigation channels, or hazards to navigation.


Are fixed navigation marks set permanently on land or water (anchored to the seabed) and like buoys help guide navigators to their destinations. They range from small structures such as single piles driven into the seabed to large light stations. Through their shape, color, pattern, topmark or light phases (if lighted); are used to mark channels, caution areas, or hazards.

Unlighted beacons are called "Daybeacons" while lighted beacons are more often simply referred to as Lighted Beacons or "Lights."

Ranges and Leading Lights

Ranges (Leading Lights) are simply (2) fixed aids to navigation that are positioned so that when in line they define a particular bearing or course. The Front Range marker is always lower and closer than the Rear Range marker and once aligned generally indicate a safe course to steer.

They can be constructed with the use of dayboards, lights, or a combination of the two and are always placed on land or fixed permanently to the seabed.

The appropriate nautical chart should be consulted when using ranges to determine the identifying characteristics and whether the range may be safely traversed. Ranges are more often than not lighted and may display lights of any color, but there are exceptions. They also display rectangular dayboards of various colors.

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