Navigational aid

A navigational aid (also known as aid to navigation, ATON, or navaid) is any sort of marker which aids the traveler in navigation, usually nautical or aviation travel. Common types of such aids include lighthouses, buoys, fog signals, and day beacons. A navigational aid (also known as aid to navigation, ATON, or navaid) is any sort of marker which aids the traveler in navigation, usually nautical or aviation travel. Common types of such aids include lighthouses, buoys, fog signals, and day beacons. According to the glossary of terms in the United States Coast Guard Light list, an Aid to Navigation (ATON) is any device external to a vessel or aircraft specifically intended to assist navigators in determining their position or safe course, or to warn them of dangers or obstructions to navigation. Lateral marks indicate the edge of the channel. The standards are defined by the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA). Approaching harbour port a vessel leaves port hand marks to port (left) and starboard hand marks to starboard (right). Port hand marks are cylindrical, starboard marks are conical. If the mark is a pillar or spar shape, then a topmark is fitted which is either cylindrical or conical as appropriate. IALA divides the world into two regions: A and B. Region B is the Americas (excluding Greenland) along with Japan, Korea and the Philippines. Region A is the rest of the world. In region A port marks are red and starboard marks green. In region B port marks are green and starboard red. Where marks are numbered red marks have even numbers and green marks have odd numbers. Where a channel divides the mark at the junction is called a 'preferred channel mark' or 'junction buoy'. The mark has the colour and shapes corresponding to the preferred channel with a band of the other colour to indicate it is the other hand mark for the subsidiary channel. In IALA region A where a minor channel branches off to port the mark at the junction would be a red cylinder with a green band. The red cylinder is a port hand mark for the main channel, the green band indicates a starboard mark for the minor channel. In IALA region B the colours (but not shapes) are reversed. Cardinal marks warn of a danger (wrecks, shoals, bends, spits etc) and indicate the safe water past the danger. There are four varieties: north, east, south and west. A north cardinal mark is placed to the north of a hazard and indicates safe water is to the north of the mark. East, south and west are placed accordingly. Cardinal marks are yellow and black with two cones at top marks. There is no difference between IALA region A and B. Black with a horizontal red band and two black balls as a top mark. The mark indicates a danger (shoal, rock, wreck etc) which is isolated with safe water all around. Red and white vertical stripes with a single red sphere for a top mark. It indicates that there is safe water all around it. The usual use is to indicate the start of a channel or port approach. Indicates a newly discovered or created danger that is not yet marked on charts (or in update notices thereto). The mark is used for a short time until the danger is either removed or else marked conventionally with lateral or cardinal marks. The mark has blue and yellow vertical stripes and a yellow and blue light. The topmark is a vertical yellow cross.