Whereas the IRPCS (International Rules for the Prevention of Collision as Sea) is consistent worldwide, buoyage systems are split into two groups, both overseen by the International Association of Lighthouse Authorities (IALA). Across Europe, Russia, India, Africa, Australia, New Zealand and much of the Western Pacific, IALA ‘A’ is used.

IALA ‘B’ is the system in North and South America, Japan, Korea, the Philippines and some of the Caribbean.

Parts of the two systems are identical, but there are also some very significant differences.

Cardinal marks
These are the same for both INLA A and INLA B. Cardinal marks warn of danger and indicate in what direction it lies.