Aids to Navigation (ATON’s) & the IALA

ATON’s - Aids to Navigation

Aids to Navigation are any sort of navigation mark which aids the mariner in the safe passage of his vessel when in confined or dangerous waters. The most common of these being buoys and beacons, but also include lighthouses, lightships, RACONs, fog signals, radio direction beacons, and range lights. They are also often referred to as “Navigation Marks,” “NavAids,” "Day Marks," or simply “Marks.”

ATON’s basically include any visible, audible, or electronically detectable navigation mark.

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) was established in 1957 as the “International Association of Lighthouse Authorities.” An association to provide nautical expertise and advice on Aids to Navigation.

Maritime experts from around the world were drawn 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.

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.

A simple rule of thumb: With a few exceptions, 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. IALA-A is the rest of the world.

Region A: Includes parts of the Atlantic Ocean, Africa, Europe, Asia, Middle East, Australia, Indian Ocean, and parts of the Pacific Ocean.

Region B: Includes parts of the Atlantic Ocean, North America, Central America and South America, Philippines, Japan, Korea, and parts of the Pacific Ocean.

The Differences

The differences between the (2) IALA systems 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.


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."

^ Scroll to Top