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If you always take your boat out in the same place and stay within sight of the shore, you become familiar with all the landmarks and always know where you are. If you go into unfamiliar waters or go out far enough that you can't see land, you need to know how to use aids to navigation, called ATONs. Short-range ATONs include buoys, daybeacons, minor lights and lighthouses. Long-range aids include satellite beacons and GPS systems. Nautical charts include symbols that clearly represent short-range ATONs.

To navigate safely from place to place on the water, you must depend on signs just as you do on land. ATONs are the road signs of the water. Two systems of marking were used in the waterways in the United States: U.S. Aids to Navigation System (USATONS), and the Uniform State Waterway Marking System (USWMS). USATONS prescribes regulatory markers and aids to navigation that mark navigable waters of the United States. USWMS prescribes regulatory markers and aids to navigation for navigable state waters. The USWMS may also mark the non-navigable internal waters of a state.

In 2003, the U.S. Coast Guard completed a merger of the USATONS and the USWMS.

Types of ATONs

The ATON system uses buoys, beacons and minor lights to mark areas such as obstructions, dangers in the water, edges of navigable channels and no-boating zones. The six types of ATONs are:

  1. Lateral marks, including preferred channel marks
  2. Safe-water marks
  3. Isolated-danger marks
  4. Range marks
  5. Information and regulatory marks
  6. Special marks

Lateral Marks

The following illustrations show what the lateral marks will look like when you enter a channel from a body of water. These illustrations are shown as they would appear on a nautical chart.

When lit, port side aids have a green light.

When numbered, port side aids have odd numbers. The numbers usually increase as you go into the channel or head upstream.

When returning from sea, keep the green port side aids on the port side of your boat.

When lit, starboard side aids have a red light.

When numbered, starboard side aids have even numbers. The numbers usually increase as you go into the channel or head upstream.

When returning from sea, keep the red starboard side aids on the starboard side of your boat.

If you are traveling down a channel and the channel splits, the following green and red markers tell you which channel is the preferred channel.

If the preferred channel is to the right, starboard, then green will be the color on top. Take the channel on your right.

These markers may be lettered, but will not be numbered.

If the preferred channel is to the left, port, then red will be the color on top. Take the channel on your left. These markers may be lettered, but will not be numbered.

Remember, when you are returning to a channel or harbor from the sea, keep the red markers on the starboard side of the boat: "Red, right, returning."

Safe-water Marks

Safe-water marks are red and white and indicate fairways, mid-channels, and offshore approach points. The water is unobstructed on all sides, and you can pass these marks on either side.

You will also see these marks if you are on offshore waters and can use them to identify how close you are to where you want to land. The lighted/unlighted buoy might show a red top-mark.

The following illustrations show the safe-water marks.

Safe-water marks may be lettered, but they will not be numbered.

Isolated-danger Marks

Isolated-danger marks indicate a danger that you can pass on all sides. This danger can be anything from a rock to a wreck. The markers are erected or moored on or near the dangers. Stay away from these markers so your boat doesn't hit any part of the danger.

The following illustrations show the isolated-danger marks.

Isolated-danger marks may be lettered, but they are not numbered.

Range Marks

Range marks and lights are a pair of aids to navigation. When the dayboards and/or lights appear to be in line with each other, you are maintaining a safe course within the channel. As you enter the channel from the main body of water, each successive mark will be higher than the one before it. Look at the appropriate nautical chart to determine if the range marks indicate the centerline of the navigable channel and also what section of the range can be safety traversed. Ranges are usually lighted and display rectangular dayboards of various colors. Ranges that are lit 24 hours a day may not have dayboards.

The following illustrations show some range marks look.

Information and Regulatory Marks

Information and regulatory marks alert you to various warnings or regulatory matters. They are identified by orange bands on the top and bottom of each buoy. A danger marker indicates something in the water that you need to steer clear of, like a rock or sandbar. An exclusion marker indicates an area to stay out of with your boat, like a swimming area or dam. A restricted operations marker indicates areas with restrictions, such as reduced speed or no anchoring.

When lighted, information and regulatory markers can display any light rhythm except quick flashing and flashing.

Special marks

Instead of helping you with navigation, these yellow marks alert you to a special feature or area, such as anchoring, traffic separation, fish net area, cable or pipeline, or military exercise areas.

Intracoastal Waterway

The Intracoastal Waterway (ICW) runs parallel to the Atlantic and Gulf coasts from Manasquan Inlet, New Jersey, to the Mexican border. ATONs marking the ICW display unique yellow symbols to distinguish them from aids marking other waters.

When following the Intracoastal from New Jersey through Texas, (south and west), always keep the yellow squares on your port and the yellow triangles on your starboard, regardless of the color of the ATON on which they appear.

A yellow horizontal band just tells you you're on the Intracoastal Waterway.

ICW beacons and buoys do not correspond to International Association of Lighthouse Authorities color system (which in the U.S. means red to starboard when returning to port) because ICW and non-ICW routes may travel next to each other in opposing directions and share the same navigation aids. Thus, when following the ICW, navigate by the yellow symbols; otherwise, navigate by the color of the aid itself.


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