Understanding Aids To Navigation

Updated 8:46 AM ET, Mon November 16, 2015

Article highlights

  • The most common markers are the red and green buoys; these mark each side of the channel.
  • Navigation aids will help "aid" you in getting from one place to another in the most direct and safest way.
  • You should always have a paper chart on board to compliment any electronic charting systems.
Headed out for a day on the water? If your boating area is along the U.S. coastline or the Inland Waterways, understanding the aids to navigation will assist you in having a safe and trouble-free trip. Aids to navigation are the road signs of the waterways. They provide a boater with the same type of information drivers get from street signs, stop signals, road barriers, detours and traffic lights. These aids may be anything from lighthouses, to minor lights, day beacons, range lights, sound signals, or lighted/unlighted buoys. Each has a purpose and keeps you out of danger as you travel from one location to another.

Understanding Aids To Navigation

What You Need To Know About Navigational Aids

If you just launched your boat from the local boat ramp and are headed out to your favorite sandbar or taking a trip along the waterway, understanding these aids to navigation are paramount. These navigation aids will help prevent you from colliding with other boats or running aground in shallow waters, and will "aid" you in getting from one place to another in the most direct and safest way. Nautical charts show the roadway of the waters. A safe boater will always have the appropriate nautical chart onboard. A paper chart should always be available to compliment any electronic charting systems on your boat.

The channels are the safest areas to operate your boat. The channel depths are such that you should not run aground if you maintain a constant watch and observe the various channel markers. The most common markers are the red and green buoys; these mark each side of the channel. Buoys are aids that float on top of the water, but are moored to the bottom. Some have a light affixed to the top; some do not. A buoy with a cylindrical shape and a conical top is referred to as a "nun". A buoy with a cylindrical shape and a flat top is called a "can".

What Are The Green Markers For?

As you leave the boat ramp of your local marina and head "toward the sea" you will encounter this series of red and green markers or buoys. Keep the green markers to the starboard (right) side of the boat as you leave the harbor and head-out on your excursion. These markers will be numbered. The green markers will have odd numbers and the red markers will have even numbers. Some of the markers may be lighted. These markers, or buoys, will be referenced on your navigation chart so you can follow your progress along the waterway. Some waterways will have fixed markers to indicate the channel. The green fixed marker will be square in shape while the red fixed marker will be a triangle. Each will be marked with a number, just like the floating buoys.

What Are The Red Markers For?

When returning back from an offshore excursion always remember the 3R Rule- Red, Right, Returning. In other words, always keep the red markers to the right side of your boat. As you leave a larger body of water, and enter the smaller body (harbor, river) of water the numbers on the markers will increase. This increase indicates that you are going further inland. There may also be green lights and red lights on the markers, so as you proceed inland, keep the red lights on your right (starboard) side and keep green lights on the left (port) side of the channel. Typically these lights will flashing in some fixed sequence. This lighting sequence will be referenced on your nautical chart so that you can keep track of your exact location.

Other Aids To Navigation

You may also encounter other multi-colored aids to navigation, fixed or floating, along the shore: These indicate preferred and secondary channels, preferred channel markers are found at the junction of navigable channels and often mark wrecks or obstructions. A vessel can pass this aid on either side, but the top color band indicates the preferred channel. If the top band of the aid is red, it is to be treated like a red marker and kept starboard (right) by the vessel returning. Fixed markers on shore, are known as Range Day boards, come in pairs; these are used to help you maintain a straight and safe course within a navigable channel. Each member of the pair is separated from the other in distance and elevation. When the two boards appear to be vertically stacked, your boat is on the range line. The colors of Range Day boards do not impact navigation - colors are simply chosen based on how well they stand out from the background scenery. Ranges may have day boards and lights or just lights. Always refer to your chart when encountering a range marker.

Non-Lateral Aids To Navigation

Other aids to navigation include markers known as "non-lateral aids to navigation". They indicate:

1.) Information or Regulatory Marks - These are orange and white in color and come with various symbols, each with their own meaning. A triangle indicates danger, alerting you to some hazard. Marks with a circle indicate areas with regulated operations, such as slow or idle speed. You should refer to your chart for detailed information about this area. A diamond shape with a cross signals that boats are prohibited from the area. Marks with a square provide helpful information such as directions, distances, and locations (like a gas dock or boat ramp).

2.) Special Aids - These Aids indicate special areas or features such as anchoring, traffic separation,
fishnet area, cables or pipelines, military exercise areas, and jetties. These marks will be all yellow, can come in a variety of shapes, and may have one black letter.

3.) State (Inland) Waters Obstruction Mark - These aids indicate to a boat operator that an obstruction to navigation extends from the nearest shore to the buoy. Do not pass between the buoy and the shore. These marks are black and white, vertically striped buoys. They may show a white reflector or display a quick-flashing white light.

4.) Mooring Buoys - While not a navigational aid, mooring buoys are worth mentioning. They are the only type of buoys to which mooring is permitted. Most mooring buoys are either privately owned or rental buoys. Permission is usually needed to use them. Mooring Buoys are white with a blue horizontal band and are cylinder or sphere shaped. They may show a white reflector or display a white or yellow light.

5.) Intracoastal Waterway Marks - The ICW runs parallel to the Atlantic and Gulf coasts from Manasquan Inlet, New Jersey to the Mexican border. Aids to navigation that mark the ICW display unique yellow symbols to distinguish them from other aids. A yellow triangle should be kept on the starboard (right) side of the vessel. Yellow squares should be kept on the port (left) side of your vessel. A yellow horizontal band provides no lateral information, but simply identifies the ICW.

Note: When following the ICW from New Jersey through Texas, keep yellow triangles on your starboard side, and yellow squares on your port side, regardless of the color of the navigation aid.

Navigation Lights

When operating your boat at night, and one of the most important aids to navigation are the navigation lights on your boat; all boats should be equipped with these colored lights: red and green on the bow (front), and white on the stern (back) of your boat. Large power boats will also have a white light amidships above the deck of the boat. The red light will display on the port side, while the green light will display on the starboard side of the boat. Understanding these light patterns on other boats as you travel at night makes clear the direction of those boats and yours as well. A green light and white light indicates the starboard side of a boat and if it is moving then it is going from your left to right. A red light and white light displays the port side of a boat, and if moving, it is going from your right to your left. If you see both a red light and a green light, slow down and take precaution, as that boat is directly in front of you. Turn your navigation lights on from sunset to sunrise and during daytime periods of reduced visibility, such as rain and fog.

Other Helpful Resources

These are the basic aids to safely navigating the waterways. If you boat in areas with commercial boating traffic, there are even more aids to navigation to learn including lighting aids to navigation on commercial ships. You should have several reference sources onboard to help you follow the "Rules of the Road ". An electronic charting program will provide some additional information. Because the exact meaning of an aid to navigation may not be clear, these other resources will be useful:

U.S. Coast Guard Aids to Navigation System- This pamphlet is designed to help the recreational boater understand the use and identification of the U/S. Aids to Navigation System.

Local Notice to Mariners - This is an excellent resource with updated information regarding changes in aids to navigation in your area, such as missing markers, changes in channel depths due to shoaling, or other obstructions, etc.

Chapman Piloting and Seamanship -This book is considered the Bible for boating safely. Every boater should have a copy on hand as it covers virtually every aspect of small boat use.


For the safety of all boaters, make sure you know your "Reds" from your "Greens" and you will always be "Right" when it comes to navigating your favorite waterways.

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