Aids to navigation

Aids to navigation (AtoN) are the buoys, beacons, lighthouses, leading lines, and electronic marks placed to guide vessels and mark hazards, channels, and landfalls. The international system is set by IALA, the International Association of Marine Aids to Navigation and Lighthouse Authorities, through the IALA Maritime Buoyage System (Recommendation R1001) and the AtoN service-level recommendations. AtoN split into floating marks (lateral, cardinal, isolated-danger, safe-water, and special buoys) and fixed marks (beacons, lights, leading lines). Each carries a defined shape, color, topmark, and light character so a mariner reads its meaning at a glance, day or night. Many now broadcast position by AIS or are augmented by racon radar transponders.