by B.J. Porter (Contributing Editor)
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Looking at a chart can be a confusing thing for the first time, but it’s not necessarily as confusing as the bewildering array of marks, floats, buoys, cans, nuns, beacons, lights and other official aids to navigation you might encounter in your travels. But there is a system, and understanding a few key concepts can clarify a lot of confusion.
“Aids to Navigation” are markers, floats, lights, or other tools used to help all mariners safely negotiate the waterways. Most aids to navigation a near shore, because that’s where most of the dangers lie. They’re placed to keep you off shoals and shallows, and in preferred channels with plenty of water for safe travel. They may also direct and separate traffic, and because they are fixed in place and marked on a chart, they can always assist you in fixing your position and determining exactly where you are.
Government agencies place and maintain the most reliable aids. You may encounter private aids, maintained by local clubs or organizations, but they’re rarely displayed on charts and may be subject to change. And not every government in the world is as standardized, and marks may be different or only supplied by locals who use the waters.
Every single mark used on a chart in U.S. waters (and most around the world) is documented, and you can get a copy for free. USCG Nautical Chart No. 1 is the reference for all charts and aids to navigation, and everyone should have a copy on board. Download it now if you don’t have it, so you can peruse it at your leisure.
For aids to navigation, pay close attention to sections P (Lights) and Q (Buoys and Beacons), though all sections have useful information. And don’t let the sheer number overwhelm you. If you stay out of busy shipping zones, most of your recreational navigation won’t see that many complex options.
In Chart No. 1 and in other places, you’ll see the phrase “lateral marks.” These are marks designed to keep you in the channel, and in navigable water and away from shoals.
They’re usually floating buoys, but they can also be posts, platforms mounted on the seabed, or even groups of pilings. They’re almost always in the water, but they can be on shore.
The important things to note are the shape and color of the mark, as that gives you a clue of its meaning.
The IALA-B marking scheme is used in North and South America and a few other places. Everywhere else, IALA-A is used, but it is similar in most respects to one major difference: the reversal of red and green. So “Red, Right, Returning” works really well in the U.S., but in Europe it will not.
In both systems, keep-to-port marks are square on top, and keep-to-starboard marks are conical.
Unless you’re crossing oceans or chartering a boat out of your home country, you’ll do all your navigation under your home scheme.
Every aid to navigation has meaning specific colors, and almost always has a number or group of letters which correspond to its identity on a nautical chart. Correctly identifying the type of aid, along with specifying its exact identity, is crucial for safe navigation.
The meaning of a mark is determined by the direction of travel – the references heading “upstream” from the sea to shore. Many colored marks will also be lit with a light the same color.
Mariners keep green marks to starboard coming in from the sea, and they keep red marks to port.
“Is there any red port left?” is a common memory aid.
When coming in from the sea, sailors keep red marks to starboard and green marks to port.
Here, “Right, right, returning” applies.
It’s not uncommon to see a buoy in the middle of a channel with color bands on it, like a rand band across a green mark. This is a mid-channel buoy and shows the preferred side to pass the marker. Heading upstream, treat the top or outside mark as the color of the buoy. So a Green/Red/Green mid channel buoy in North America should be taken to port when coming in from the sea.
Low visibility conditions like darkness and fog may make colors tricky to pick out, and color blind people can’t often tell red from green. Port marks are always square on the top, and starboard marks are conical or triangular. So floats will be cylinders (port) or have a cone on top of them (starboard).
Post markers will have a square or triangle. This is the same for both IALA schemes.
Marks are usually numbered, but may also have letters. These correspond to the marks on a chart, which makes specific identification precise and easy.
Port marks are odd numbered, and starboard marks are even. In most cases, the numbers increase from the entrance of a harbor or bay. Be aware there may be sub-navigational areas in a larger region where the numbers re-start at one and keep going up.
A good example is Narragansett Bay in Rhode Island, where you’ll find a green mark number 1 down at the entrance of the bay. But further up the bay, you’ll find other G1 marks, and these re-start numbering because you’ve entered a different regional bay, such as Greenwich Bay or Mount Hope Bay, or entered a river such as the Warren River.
So the numbers and letters will be unique to an area around where you’re looking on a chart, but you may find them repeating as you move around the local waters.
Not all buoys are lit, but in high-traffic areas many are. The lights will match the color of the mark, and will have a distinctive flashing pattern, timing, or sequence. Some are simple on/off lights, cycling for a set number of seconds. But others may have a combination of flashing patterns to make them more distinct, such as a double flash followed by a pause, then a single flash (2 + 1).
For low visibility conditions, many marks have a sound. This may be a bell, whistle, gong or horn and should repeat. Depending on the sound and how it’s made, it may not always be a consistent repetition. In rough conditions, you may hear a bell more frequently as waves rock the buoy, for example.
Next to every lateral mark with a sound of light is a small textual description on your chart. The abbreviations are listed in Chart No. 1, but most of them are pretty clear, like “FL R 2.5s Bell” for “flashing red every 2.5 seconds with a bell.”
So how do you use all these aids to navigation to get safely to your destination and back? There are two primary ways – for planning your trip and for navigating on the way using safe water lateral marks to negotiate shallows and channels.
When you plot your course, review any marks you might pass along the way. Make a list, with their descriptions, numbers, sounds, and lights. This gives you a sense of what to look for, and if you know your next waypoint is at the mark “G1” and it’s a flashing green light every 2.5 seconds, you can confirm that mark as you approach it night or day.
As you travel to your destination, identify marks as you pass them from the descriptions in your charts. Positive identification of a mark provides a precise location fix, and the mark itself indicates how to pass it safely and what to watch out for during navigation.
We have only covered the fundamentals of lateral marks used for navigation aids in this article. We’ll get into more advanced types of aids to navigations, like safe water marks, radar beacons, lighthouses, and range markers in future articles in this series.
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The equipment provided on a vessel that helps the ship’s navigators navigate safely is called Navigational Aids. Most of them are electrical or electronic equipment but still some equipment does not require electrical power for operation. Aids to Navigation are placed along coasts and navigable waters as guides to mark safe water and to assist mariners in determining their position in relation to land and hidden dangers. Each aid to navigation is used to provide specific information. Several aids to navigation are usually used together to form local assistance to the navigation system that helps the mariner follow natural and improved channels. Such aids to navigation also provide a continuous system of charted marks for coastal piloting. Individual aids to navigation are used to mark landfall from seaward, and to mark isolated dangers.
For safe, efficient economic and comfortable travel of vessels in rivers, channels harbours and along lake and ocean shores navigational aids are necessary. The purposes of navigational aids are to avoid dangerous zone, follow a proper harbour approach and locate the port during the night and bad weather conditions. Aids to Navigation are placed along coasts and navigable waters as guides to mark safe water and to assist mariners in determining their position in relation to land and hidden dangers. Each aid to navigation is used to provide specific information. Unlike the roads and highways that we drive on, the waterways we go boating on do not have
road signs that tell us our location, the route or distance to a destination, or of
hazards along the way. Aids to Navigation System is intended for use with nautical charts, which provide valuable information regarding water depths, hazards, and other features that you will not find in an atlas or road map.
A virtual aid to navigation itself does not physically exist unlike buoys and beacons but comprises a signal broadcast to a location in a waterway. It can be described as digital information transmitted from an Automatic Identification System (AIS) station located elsewhere for a specified location without being itself present in that specified location or simply stated, as an electronic virtual marker of a hazard. The basic symbol of a virtual AiS aid to navigation looks like a diamond shape with a crosshair at the centre on ECDIS or radar.
The term “aids to navigation” encompasses a wide range of floating and fixed objects (fixed meaning attached to the bottom or shore), and consists primarily of:
Different airports operate under different conditions. Smaller airports (in size and level of air traffic) may only operate during daylight hours meaning they require less additional guidance and support and may only need typical runway markings and airfield lighting. Larger commercial airports will be required to operate during the night-time hours and, therefore, are obliged to be sufficiently equipped with navigational aids to support take-offs, landings and manoeuvres. The various forms of Navaids all work in different ways to deliver the same result. ILS systems focus on ensuring a smooth and safe landing for all aircraft by offering accurate horizontal and vertical support during their approach and landing. Their function is critical during periods of low/poor visibility. DME systems utilize ultra-high frequencies (UHF) to receive and send signals to and from the aircraft, enabling it to calculate its flight position and determine a time-to-station value based on the time it takes for the aircraft’s DME transceiver to receive a response from the DME
station. NDBs are ground-based transmitters that support and aid aircraft throughout their approach by providing the direction to the airport from their current position on their flight deck equipment. VORs similarly enable the aircraft to determine its position from the destination using Omnidirectional signals from the VOR system. DVORs are specifically used during low/poor visibility conditions. TACANs are used primarily by the Navy (but are used for civil applications) and are a modern adaption of the VOR (and deliver the same functionality).
We can provide a whole package of tools to assist airports with the aerodrome
safeguarding, the design and preparation of instrument approach procedures, studies for the definition of equipment specification, and system design — complemented where necessary by sophisticated computer modelling techniques for surveying and selecting sites for navaids and the protection of ILS sensitive areas.
Navigational aids are a crucial piece of equipment used for assisting the safe and efficient landing of aircraft which need to locate their landing zone accurately during low light hours and avoid high risk/danger during their approach.
That’s why we ensure that our navaid equipment and systems accurately measure the distance of aircraft and transmit signals to inform on landing locations, track the position of the aircraft while it’s in flight to ensure it’s staying on course and assist the craft during its descent and landing process.
Many of the early age navigation aids have become obsolete and ceased to be used but some are regarded as essential items and are still used on ships.
Depending on where you boat in America, you may see several differences in how navigational marks are coloured, numbered, or lighted. Regardless of the location, buoys and beacons are placed in very specific locations, to mark either a particular side of a waterway or some other navigational feature. The primary system in use is referred to as the “U.S. Aids to Navigation System”. The U. S. Coast Guard maintains this system in conformance with the International Association of Lighthouse Authorities (IALA), which is an international committee which seeks to ensure safe navigation, primarily through the use of common navigation aids and signals. The “LATERAL” system is the familiar RED RIGHT RETURNING system, meaning that on all navigable waters returning from sea, the red even-numbered marks are on the starboard (right) side of the channel and the green odd-numbered marks are on the port (left) side of the channel. Numbers on the marks ascend when travelling from sea to harbour — if you don’t have a compass and become disoriented on the water, you will always know you are heading upstream if the buoy numbers get larger as you travel.
Port side numbered aids are green in colour, odd-numbered and may be lighted. Port side marks are located on the left side of the waterway as you travel upstream, and the buoy numbers will increase as you head upstream. (Chart depictions are shown next to the marks) Port-Side Buoys have a cylindrical above-water appearance, like a can or drum floating on its axis. Commonly referred to as “CAN” buoys. Beacons-Port side beacons have square marks attached to them, with two shades of colour and a reflective border.
Starboard aids are red in colour, evenly numbered and will be on your right side as you travel upstream. Buoy numbers increase as you head upstream, and may have a red light. Starboard-side buoys have an above-water appearance like that of a cylinder topped with a cone, pointed end up. The cone may come to a point or be slightly rounded. Commonly referred to as “NUN” buoys. Starboard-side Beacons have triangular marks attached to them, with two shades of colour and a reflective border.
For the sea buoys that delineate channels off the coast of the United States, and for the Intracoastal Waterway (ICW), red is on the right (shore side) when proceeding clockwise around the U. S. from the East Coast to the Gulf Coast, or proceeding north along the West Coast. ICW marks are further identified by a small yellow reflector at the bottom of the mark. The same port and starboard marks shown above will look like the following.
Numbers on the marks ascend when travelling in this direction. Where the IALA-B and ICW marks meet, one must be very careful to observe the change in meaning by referral to local charts.
Navigational aids are a crucial piece of equipment used for assisting the safe and efficient landing of aircraft which need to locate their landing zone accurately during low light hours and avoid high risk/dangers during their approach. Everybody, both onshore and at sea, has a responsibility for improving our ship's safety level. Aids to navigation, also known as AtoN, are important tools of navigation that enhances safety and can act as good safety barriers. Aids to navigation help ship navigating officers in finding and safely navigating a narrow channel in a wide expanse of water. Virtual aids to navigation are the potential in enhancing safety and their use brings us several advantages. For the safe and efficient navigation of vessels, it is important that the vessels recognize their accurate position and maintain a fixed course. Aids to navigation are established to assist vessels in the wide ocean where landmarks are not visible, areas crowded with vessels with narrow channels and areas with dangerous obstacles. Vessels ascertain their positions by the lights shape of objects, colours sound and radio waves．
1. https://en.wikipedia.org/wiki/Navigational_aid
2. https://www.marineinsight.com/marine-navigation/virtual-aids-of-navigation-are-important-for-ships
3. https://www.boatus.org/study-guide/navigation/aids
4. https://www.tokokai.org/en/role-types-aids-navigation/
5. https://www.systemsinterface.com/products/navaids/
6. https://www.slideshare.net/bhavikpatel19196/navigational-aids
7. Class Note Provided by
Captain Md. Arif Mahmud
Assistant Professor
Department of Maritime Science
For more Marine Aids to Navigation Solutionsinformation, please contact us. We will provide professional answers.