A navigational aid (NAVAID), also known as an aid to navigation (ATON), is any type of signal, marker, or guidance device that aids the traveler in navigation, usually in maritime or aviation. Common types of such aids include lighthouses, buoys, fog signals, and day signals.
On waterways, there are no road signs to tell us our location or distance to a destination or the hazards along the way. Therefore, safe waters have been marked with buoys and beacons by navigation authorities for hundreds of years.
Lateral markers indicate the edge of the fairway. Standards are set by the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA). The IALA divides the world into two regions:
A: The rest of the world
port marks red and starboard marks green
B: American continent (excluding Greenland) plus Japan, Korea, and the Philippines
port marks green and starboard marks red
Port hand signals are cylindrical, starboard hand signals are conical.
- warn of danger (wrecks, shoals, curves, spits, etc.)
- indicate safe water behind the danger
- yellow and black with two cones at the upper marks
- no difference between IALA region A and B
Isolated hazard mark
- black with a horizontal red stripe and two black cones as top marks
- indicates hazard (shoal, rock, wreck, etc.) that is isolated and has safe water all around it
Safe water sign
- red and white vertical stripes with a single red ball as a top sign.
indicates safe water all around
- Common at the beginning of a navigation channel or harbor entrance
- newly discovered or created hazard not yet shown on nautical charts
- used for a short time until the hazard is either eliminated or marked in a conventional manner with lateral or cardinal markings - blue and yellow vertical stripes and a yellow and blue light
- Yellow with "X" as the top mark
- Floating areas, anchorages, pipelines
- different colors depending on the angle of approach
- white for safe fairway
- red or green for outside the safe fairway
- IALA prescribes that colors of lights must correspond to the color scheme of the respective region (A or B)
If there is no real AtoN (e.g. for short-term marking of a wreck), a "virtual AIS AtoN" is used. Virtual AtoNs mark their messages as repeats to indicate that the location of the station is not the location of the AtoN.