The marine buoy system is internationally characterized, with various buoy systems across the world historically being inconsistent. In 1971, the Technical Committee of the International Association of Marine Aids to Navigation classified different types of marine buoys into two systems: System A, which combines side and cardinal markers; and System B, which is a side marker system. In November 1980, during the 10th International Aids to Navigation Conference held in Tokyo, Systems A and B were merged into a unified system, encompassing five types of markers: side, cardinal, isolated hazard, safe water, and general markers. The side markers in Systems A and B indicate opposite contents, while the other four types are consistent. Cardinal markers are established in the four quadrants from true north to northeast, northeast to southeast, southeast to southwest, and southwest to northwest, centered around hazards or hazard areas, indicating navigable waters on the same side as the cardinal marker. Isolated hazard markers are placed on or as close as possible to hazards, indicating ships should avoid navigation. Safe water markers are placed in the center or along the centerline of the channel, allowing navigation around the marker. Markers are used to indicate specific water areas or features, such as quarantine anchorage, no-go zones, and marine operations.
European countries, African nations, Gulf region states, as well as certain Asian countries and Australia and New Zealand adopt System A, referred to as the A Region; American countries, Japan, South Korea, and the Philippines use System B, known as the B Region. Based on the principles of the A Region for maritime aids to navigation in international sea areas, China established the National Standard for Maritime Aids to Navigation in Chinese Sea Areas and the National Standard for Inland Waterway Aids to Navigation in China in 1984, which have been implemented (see Maritime Aids to Navigation in Chinese Sea Areas and Inland Waterway Aids to Navigation in China).
