The waters of the United States and its territories are marked to assist navigation by the U.S. Aids to Navigation System (ATONS). This system employs a simple arrangement of color, shapes, numbers, and light characteristics to mark navigable channels, waterways, and obstructions adjacent to these.
Aids to Navigation can provide a boater with the same type of information that (car) drivers get from street signs, stop signs, road barriers, detours, and traffic lights. These aids may be anything from lighthouses to minor lights, day beacons, range lights, and sound signals, to lighted or unlighted buoys. Each has a purpose and helps in determining location, getting from one place to another or staying out of danger. The goal of the U.S. Aids to Navigation System is to promote safe navigation on the waterway.
The U.S. Aids to Navigation System is intended for use with Nautical Charts. Charts are one of the most important tools used by boaters for planning trips and safely navigating waterways. Charts show the nature and shape of the coast, buoys, and beacons, depth of water, land features, directional information, marine hazards, and other pertinent information.
The primary components of the U.S. Aids to Navigation System are beacons and buoys.
Beacons are aids to navigation structures that are permanently fixed to the earth’s surface. The range from lighthouses to small, single-pile structures and may be located on land or in the water. Lighted beacons are called lights; unlighted beacons are called day-beacons. Beacons exhibit a day-mark to make them readily visible and easily identifiable against background conditions. Generally, the day-mark conveys to the boater, during daylight hours, the same significance as does the aid’s light or reflector at night.
Buoys are floating aids that come in many shapes and sizes. They are moored to the seabed by concrete sinkers with chain or synthetic rope moorings of various lengths connected to the buoy’s body. They are intended to convey information to the boater by their color and shape, by the characteristics of visible or audible signal, or a combination of two or more such features.