Aids to Navigation

Prior to the mid-1970’s, there were over 30 different navigation systems in use around the world. To reduce confusion, IALA established two systems of buoyage for conveying navigation information to mariners. The IALA System A and B were established, with the U.S. complying with the IALA B System. The IALA-A and IALA-B systems use the Lateral and Cardinal Systems to define the conventional direction of buoyage, and to mark channels with ATON. “Lateral significance” or “cardinal significance” means that the rules for the Lateral or Cardinal System apply in that instance. However, if something has no lateral or cardinal significance, the respective system’s rules do not apply to the situation. The differences between the markings and conventions used in the Lateral and Cardinal Systems are discussed in the following paragraphs. Table 2-1 briefly describes the IALA Systems A and B:

Table 2-1 — IALA-A and IALA-B Systems

In the lateral system, buoys and beacons indicate the sides of the channel or route relative to a conventional direction of buoyage (usually upstream). They also mark junctions, a point where two channels meet when proceeding seaward; or bifurcations, the point where a channel divides when proceeding from seaward, or the place where two tributaries meet. In U.S. waters, ATON use (with few exceptions) the IALA-B system (see Table 2-1) of lateral marks, arranged in geographic order known as the “conventional direction of buoyage” (Figure 2-1). Under this, the memory aid 3R Rule of “red, right, returning” applies when a vessel is returning from seaward. This means, when returning from sea, keep red markers to the right of the vessel from: (01) North to south along the Atlantic Coast, (02) South to north and east to west along the Gulf Coast, (03) South to north and east to west along the Pacific Coast, (04) East to west in the Great Lakes except for Lake Michigan which is north to south.

The Cardinal System uses a buoy to indicate the location of a danger relative to the buoy itself. In the U.S., the USWMS uses cardinal marks on waters where a state exercises sole jurisdiction. The colors of these marks differ from those of IALA. For instance, a white buoy with a black top indicates unsafe water to the south and west. Various countries throughout the world, including Canada, Bermuda, and the Bahamas, also use cardinal marks along with lateral marks. Cardinal marks are not used on waters where the U.S. Coast Guard maintains short-range ATON.

Aids to navigation have many different characteristics. An aid’s color, size, light, and sound signify what mariners should do when they see it. Characteristics of short-range aids used in the U.S. are described in the following paragraphs.

The location and the intended use determine which one of the two types of ATON will be placed in a spot or waterway: (01) Floating (buoy), (02) Fixed (beacon).

Solid red ATON buoys and beacons bear even numbers and all solid green ATON bear odd numbers. No other ATON are numbered. When proceeding from seaward toward the direction of conventional navigation, the numbers increase. Numbers are kept in approximate sequence on both sides of the channel. Letters may be used to augment numbers when lateral ATON are added to channels with previously completed numerical sequences. For instance, a buoy added between R"4" and R"6" in a channel would be numbered R"4A". Letters will also increase in alphabetical order. Not every buoy or beacon is numbered. Preferred channel, safe water marks, isolated danger, special marks, and information/regulatory ATON use only letters.”

During daylight hours, the color of an ATON indicates the port or starboard side of a channel, preferred channels, safe water, isolated dangers, and special features. Only red or green buoys, or beacons fitted with red or green dayboards, have lateral significance.

Shapes of buoys and beacons help identify them from a distance or at dawn or dusk, when colors may be hard to see. Like other characteristics of ATON, mariners should not rely solely on shape to identify an aid.

Cylindrical buoys, often referred to as “can buoys,” are unlighted ATON. When used as a lateral mark, they indicate the left side of a channel or of the preferred channel when returning from seaward. They are painted solid green or have green and red horizontal bands; the topmost band is always green. Can buoys are also used as unlighted special marks and will be colored based on their use (Figure 2-2).

Conical buoys, often referred to as “nun buoys,” are unlighted ATON. When used as a lateral mark, nun buoys indicate the right side of a channel or of the preferred channel when returning from seaward. They are painted solid red or red and green with horizontal bands and always with a red topmost band. Nun buoys are also used as unlighted special marks and will be colored based on their use (Figure 2-2).

[Lettered on the illustration: CAN BUOY (LEFT) NUN BUOY (RIGHT)]

The Coast Guard and other agencies place (station) specialty buoys for operational and developmental uses, and for research purposes. In many instances, the buoy used is a standard buoy modified for specialized use. There are several examples of specialty buoys: (01) Fast water buoys, (02) Discrepancy buoys, (03) Weather/oceanographic buoys, (04) Mooring buoys.

Beacons have dayboards attached to a structure. When returning from sea, a triangular shaped dayboard marks the starboard side, and a square shaped dayboard marks the port side of the channel (see Figure 2-3).

Though there are white and yellow lights, only ATON with green or red lights have lateral significance. When proceeding in the conventional direction of buoyage, ATON will display the following light colors: (01) Green, (02) Red, (03) White and yellow.

Green lights mark port sides of channels and wrecks or obstructions. When proceeding from seaward, these aids are passed by keeping them on the port side. Green lights are also used on preferred channel marks where the preferred channel is to starboard. When proceeding along the conventional direction of buoyage (from seaward), a preferred channel mark fitted with a green light would be flashing 2+1 with the color of the preferred channel being kept on the port side.

Red lights mark starboard sides of channels and wrecks or obstructions. When proceeding from seaward, these aids would be passed by keeping them on the starboard side. Red lights are also used on preferred channel marks where the preferred channel is to port. When proceeding along the conventional direction of buoyage (from seaward), a preferred channel mark fitted with a red light would be flashing 2+1 with the color of the preferred channel kept on the starboard side.

White and yellow lights have no lateral significance. However, the characteristic (rhythm) of the light does give information such as safe water, danger, or special purpose. The publication called Light List, discussed in Section D of this Chapter, provides more details.

Lights are installed on ATON to provide signals to distinguish one navigation light from another, or from the general background of shore lights.

Lights displayed from ATON have distinct characteristics which help in identifying them (Figure 2-4). ATON with lateral significance display flashing, quick, occulting, or isophase light rhythms.

To identify a light, the following information should be determined:

Though not a requirement of IALA B system, in the U.S., some ATON have sound signals to provide information to mariners during periods of restricted visibility. Different types of devices are used to produce these sounds. Sound signals may be activated as follows: (01) Continuously (bell, gong, or whistle buoy), (02) Manually, (03) Remotely, (04) Automatically (when equipped with a fog detector). Sound signals can be identified by their tone and phase characteristics. Horns, sirens, whistles, bells, and gongs produce distinct sound signals. The sound signal characteristics for specific ATON are briefly described on the chart, and in length in Column 8 of the Light List. Unless it is specifically stated that a signal “Operates Continuously” or the signal is a bell, gong, or whistle, signals will only operate in fog, reduced visibility, or adverse weather.

NOTE

A bell, gong, and whistle buoy are activated by the motion of the sea and may not produce a sound signal in calm seas.

Most minor ATON (buoys and beacons) are fitted with retroreflective material to increase their visibility at night. While this material does not produce light on its own, when illuminated by a light source (searchlight), it reflects the light back towards the operator with great intensity. In most cases, the color of the reflective material panel is the same as the surface it covers (red on red, green on green). Numbers and letters found on buoys will be silver/white. Daybeacons are outlined with retroreflective material and will be identified with numbers or letters made of the same color as the beacon (Figure 2-11). Exceptions are found on some aids.

While proceeding in the conventional direction of buoyage in IALA System B, boat crews will see the following ATON:

MEMORY

Red, Right, Returning.

AID

Red buoys and beacons with triangular shaped red dayboards mark the starboard side of a channel when returning from seaward. This is the red, right, returning rule. ATON displaying these characteristics are kept to starboard when returning from seaward.

Green buoys and beacons with square shaped green dayboards mark the port side of a channel when returning from seaward.

Red and green, or green and red, horizontally banded buoys and beacons are called preferred-channel marks. They are used to indicate a channel junction or bifurcation (point where a channel divides or where two tributaries meet). They may also mark wrecks or obstructions and may be passed on either side. When returning from sea, and the topmost band is: (01) Green: keep the aid to port to follow the preferred channel, (02) Red: keep the aid to starboard to follow the preferred channel.

Safe water marks are buoys with alternating red and white vertical stripes, and beacons with red and white vertically striped dayboards (Figure 2-5). They also mark a mid-channel, fairway, channel approach points and the “In” and “Out” channels of a “Traffic Separation Scheme.” See buoy “N” in (Figure 2-5). If lighted, they will display a white light with the characteristic Morse Code “A”. Safe water buoys (lighted or not) should be fitted with a red sphere as a visually distinctive top mark. Safe water marks are not laterally significant.

Black and red horizontally banded buoys are called “Isolated Danger Marks”. They are used to mark isolated dangers (wrecks or obstructions) which have navigable water all around. Isolated danger marks display a white light with a “group-flashing” characteristic; and are fitted with a visually distinctive topmark, consisting of two black spheres, one above the other (Figure 2-11).

NOTE

This buoy marking system is not used in the Western River System.

Yellow buoys and beacons are called “special marks”. They mark anchorages, dredging/spoil areas, fishnet areas, and other special areas or features. When lighted, special marks will display a yellow light with a Fixed (“F”) or Flashing (“Fl”) characteristic. Special marks may also be used to mark the center of the traffic separation scheme.

Information and regulatory buoys and beacons indicate various warnings or regulatory matters. They are colored with white and orange shapes (Figure 2-11). They will only display a white light and may display any light rhythm except quick flashing.

Beacons with no lateral significance may be used to supplement lateral ATON outside normal routes and channels. Daymarks for these aids are diamond shaped and will either be red and white, green and white, or black and white (Figure 2-11).

Buoys are floating ATON anchored at a given position to provide easy identification by mariners. The significance of an unlighted buoy can be determined by its shape. These shapes are only laterally significant when associated with laterally significant colors such as green or red. Buoys are useful ATON, but should never be relied upon exclusively for navigation. When a buoy is “watching properly”, it is marking its charted position “on Station” and properly displaying all other distinguishing characteristics. Heavy storms, collisions with ships, and severe ice conditions may move a buoy “off Station”. Heavy storms may also shift the shoal a buoy marks into the channel. It is important to remember, even heavily anchored buoys fail.

Beacons are fixed ATON structures attached directly to the earth’s surface. The design, construction, and characteristics of these beacons depend on their location and relationship to other ATON in the area. Strictly defined, a beacon is any fixed unlighted ATON (daybeacon) or minor light (lighted) ATON of relatively low candlepower. The following types of beacons are used in the U.S.: (01) Daybeacons, (02) Lighted beacons (minor lights), (03) Major lights, (04) Light towers.

Daybeacons are unlighted fixed structures fitted with a dayboard for daytime identification. To increase their visibility in darkness, dayboards are fitted with retroreflective material. Daybeacons are built on different types of structures: (01) Single pile with a dayboard on the top, (02) Multi-pile structure, (03) Tower, (04) Structure of masonry or steel.

Just as daybeacons are sometimes substituted for unlighted buoys, lighted beacons are substituted for lighted buoys. Their structures are similar to daybeacons (Figure 2-6). Lighted beacons are used with other lateral aids (buoys) marking a channel, river, or harbor. In most instances, the lights have similar candlepower to those lights on buoys in the same area. They can also be used to mark isolated dangers.

Major lights display a light of moderate to high candlepower. They may also have high intensity audible signaling devices, radiobeacons and radar beacons (RACONs). Major light structures, lighthouses for instance, enclose, protect, and house their signaling devices. In their surroundings, major light structures have visually distinctive appearances. Determining whether a light is major, or minor, depends upon its candlepower and the luminous range of the light. A light’s category may change if fitted with a higher or lower candlepower light. Major lights rarely have lateral significance and fall into two broad categories. They are used as coastal or seacoast lights and are often referred to as primary ATON. They mark headlands and landfalls and are designed to assist vessels during coastal navigation or when approaching from seaward. They are also used as “Inland Major Lights” and are found in bays, sounds, large rivers, and coastal approaches. As an inland major light, they serve a variety of functions: (01) Obstruction mark, (02) Sector light, (03) Reference mark from which a visual bearing or range can be obtained.

Besides the main signal light, additional features found on some major lights help provide more detailed information concerning the surrounding area (colored light sectors) or provide a secondary light source should the primary lantern fail.

Sector lights are sectors of color that are displayed on lantern covers of certain lighthouses to indicate danger bearings. Sector bearings are true bearings and are expressed as “bearings from the vessel towards the light.” A red sector indicates a vessel would be in danger of running aground on rocks or shoals while in the sector. Red sectors may be only a few degrees in width when marking an isolated obstruction (Figure 2-7)

Reduced intensity emergency lights are displayed if the primary lights are extinguished. They may or may not have the same characteristics as the primary lights. The characteristics of emergency lights are listed in Column 8 of the Light List (Figure 2-7).

Light towers replaced lightships and are located in deepwater to mark shoals and heavily traveled sea lanes. The foundation or legs of these towers are fixed to the bottom. They are equipped with signals comparable to major lights.

Ranges are pairs of beacons located to define a line down the center of a channel or harbor entrance. They are usually lighted and arranged so that one mark is behind and higher than the other mark. When both markers of the range are in line, a vessel’s position is along a known LOP. Ranges are located on specially built structures, existing ATON structures, or structures such as buildings or piers. Ranges are found in entrance channels to harbors, piers, or successive straight reaches. Range marks are located so that when viewed from the channel the upper mark is above, and a considerable distance beyond, the lower mark.

CAUTION !

The limits of a range can be determined only by checking the chart. They show the fairway or reach of the channel marked by the range. This area will be marked by a leading line (solid line) on the chart. At the turn, the range will be marked by a dotted line (Figure 2-8).

Ranges are considered to be non-lateral ATON. Some ranges have rectangular daymarks that are striped in various colors (Figure 2-11). Most are lit 24 hours per day and may display either red, green, or white lights or combinations of the same. The Light List should be consulted for the light characteristics and color combinations displayed on the daymarks.

Some structures have a directional light, a single light with a special lens, with a narrow white light beaming in a specific direction. On either side of the white beam is a red or green light. The width of the sector varies with the particular location. The Light List and chart should be checked for specific information.

Extending some 2,400 miles along the Atlantic and Gulf coasts of the U.S., the Intracoastal Waterway (ICW) is a largely sheltered waterway, suitable for year-round use. ATON used to mark the ICW use the same coloring, numbering, and conventional direction of buoyage found in the U.S. ATON System with the following additional characteristics: (01) Special markings consisting of yellow squares and triangles are used so that vessels may readily follow the ICW, (02) The yellow square shows that the aid should be kept on the left side when traveling north to south/east to west, (03) The yellow triangle shows that the aid should be kept on the right side when traveling north to south/east to west, (04) Non-lateral aids in the ICW, such as ranges and safe-water marks, are marked with a yellow horizontal band.

The western rivers marking system is used on the Mississippi River and tributaries above Baton Rouge, Louisiana, and certain other rivers which flow towards the Gulf of Mexico. The western rivers system varies from the U.S. ATON System as follows: (01) Buoys are not numbered, (02) Lighted beacons and daybeacons are numbered but have no lateral significance. (The numbers relate to the distance up or downstream from a given point in statute miles), (03) Red and green diamond-shaped daymarks, as appropriate, are used to show where the channel crosses from one side of the river to the other, (04) Lights on green buoys and beacons are colored green or white (for crossings) and have a flashing (Fl) characteristic, (05) Lights on red buoys and beacons are colored red or white (for crossings) and have a group flashing (Gp Fl) characteristic, (06) Isolated danger marks are not used.

The Uniform State Waterway Marking System (USWMS) is designed for use by many types of operators and small vessels on lakes and inland waterways not shown on nautical charts. The conventional direction of buoyage in the USWMS is considered upstream or towards the head of navigation. This system has two categories of aids: (01) System of ATON compatible with and supplements the U.S. lateral system in states’ waters, not federal jurisdiction, (02) System of regulatory markers that warn of danger or provide general information and directions (Figure 2-11).

There are three USWMS variations to the U.S. ATON System: (01) On a well-defined channel, solid-colored red and black buoys are established in pairs (gate buoys), marking each side of the navigable channel, (02) The color black is used instead of green, (03) The shape of the buoy has no significance.

When there is no well-defined channel or when there is an obstruction whose nature and location allows it to be approached by a vessel from more than one direction, ATON with cardinal marks may be used. The USWMS provides for three aids with marks that have the following significance: (01) A white buoy with a red top represents an obstruction and the buoy should be passed on the south or west, (02) A white buoy with a black top represents an obstruction and the buoy should be passed to the north or east, (03) A red and white vertically striped buoy indicates an obstruction exists between that buoy and the nearest shore.

USWMS regulatory marks are white with two international orange horizontal bands completely around the buoy circumference. One band is near the top of the buoy while the second band is just above the waterline. Geometric shapes are placed on the buoy’s body and are colored international orange (Figure 2-9). There are four basic geometric shapes authorized for these marks and each one has a specific meaning associated with it. These include the following: (01) A vertical open-faced diamond shape having a cross centered in the diamond means that vessels are excluded from entering the marked area, (02) A vertical open-faced diamond shape means danger, (03) A circular shape indicates a control zone where vessels in the area are subject to certain operating restrictions, (04) A square or rectangular shape is used to display information such as direction and/or distances to a location. (Information and regulatory marks can also be used in waters outside USWMS waters (e.g., federal channels which use the U.S. ATON system).

NOTE

Regulatory marks are displayed on beacons as well as buoys.

Mooring buoys in USWMS are white with a horizontal blue band midway between the waterline and the top of the buoy, and display a slow-flashing white light when lighted. Mooring buoys in federal waters (U.S. ATON system) also display white with a horizontal blue band.

RACON is an acronym for Radar Beacon. These beacons transmit a Morse Code reply when triggered by a boat’s radar signal. This reply “paints” the boat’s radar screen in the shape of dashes and dots representing a specific Morse Code letter, always beginning with a dash. The “paint” signal appears on the radar screen showing the Morse Code signal beginning at a point just beyond the location of the RACON transmitter location and extending radially for one to two nautical miles. Transmission characteristics of RACONs may be found in the appropriate Light List. RACONs are shown on nautical charts with the letters “RACON” and a circle. RACONs are especially useful when trying to distinguish navigation aids from other contacts in congested areas. They can be found on both buoys and fixed structures.

The Automated Identification System (AIS) is an internationally adopted radio communication protocol that enables the autonomous and continuous exchange of navigation safety related messages amongst vessels, lifeboats, aircraft, shore stations, and aids to navigation. AIS equipped aids and stations broadcast their presence, identity (9-digit Marine Mobile Service Identity (MMSI) number), position, and status at least every three minutes or as needed. All three AIS ATON variants can be received by any existing AIS mobile device, but they would require an external system for their portrayal (i.e., ECDIS, ECS, radar, PC). Table 2-2 provides amplifying information AIS ATON electronic charting symbols now in use. How they are portrayed currently varies by manufacturer, but the future intention is for the portrayal to be in accordance with forthcoming international standards. There are numerous applications of virtual aids to navigation. They are used not only to mark specific locations like beacons or buoys do, but also to mark lines, areas and other forms. They are not intended to replace physical aids to navigation, but to complement or supplement existing marks to improve the safety of navigation.

A ‘Real’ AIS ATON Station is a physical aid to navigation fitted with an AIS device. For practical or economic reasons it may not be appropriate to fit an AIS to an ATON. In this case, the ‘Synthetic’ AIS approach may be taken. There are two types of synthetic AIS ATON, ‘Monitored’ and ‘Predicted’. (01) A ‘Monitored Synthetic AIS ATON’ is transmitted from an AIS Station that is located remotely. The ATON physically exists and there is a communication link between the AIS Station and the ATON. The communication between the ATON and AIS shall confirm the location and status of the ATON, (02) A ‘Predicted Synthetic AIS ATON’ is transmitted from an AIS Station that is located remotely. The ATON physically exists but the ATON is not monitored to confirm its location or status. Predicted Synthetic AIS ATON should not be used for floating aids to navigation.

A Virtual AIS ATON is transmitted from an AIS station to establish an aid to navigation that does not physically exist. In this case, a digital information object will appear on the navigational system for a specified location, even though there is no physical ATON. A nearby base station or ATON station could broadcast this message. The AIS message will clearly identify this as a Virtual AIS ATON.

A Virtual ATON will not be visible on the displays of many ships and, if visible, the symbols may differ from one display to another. The consequences may be confusion and lack of information for the user, as well as undermining confidence in ECDIS, the chart, and other systems. Other limitations include: (01) Global navigation satellite system (GNSS) vulnerability, (02) Susceptibility to spoofing and jamming.

Table 2-2 — AIS or Virtual Aids to Navigation (ATON)

NOTE

The symbols used in the chart above are examples of virtual ATON and there is no mandate for an international standard. Different electronic navigation systems may use different symbols.

This publication includes detailed descriptions of both short-range ATON, radionavigation systems, and complete lists of lights for the area.

The aids in the Light List are listed so that seacoast aids appear first, followed by entrance and harbor aids from seaward to the head of navigation. Light List numbers (LLNR) are assigned to aids for easy reference and appear in sequence from: (01) North to south along the Atlantic Coast, (02) South to north and east to west along the Gulf Coast, (03) South to north along the Pacific Coast.

The general information section offers information about the layout and organization of the Light List. It describes the U.S. system of ATON and its characteristics and provides a glossary of terms.

To determine the position and characteristic of Ocean City Inlet Jetty Light the following procedures should be taken to find this information in the Light List:

In this case, the position of the light is 38o19.5' N, 75o05.1' W; and the light characteristic is Isophase white 6 seconds.

NOTE

In the index below, the Ocean City Inlet Jetty Light has what appear to be two LLNRs, 225 and 4720. Having two LLNRs means that this aid will be listed as a “seacoast” aid using LLNR 225, and again as a “harbor entrance” aid under Ocean City Inlet Jetty Light using LLNR 4720. Seacoast ATON are

O Oak Creek............................................26205 Oak Island Channel .............................30415 Oak Island Light......................................810 Oak Island Radiobeacon..........................815 Occohannock Creek.............................21695 Occoquan River...................................18265 Ocean City Inlet.....................................4720 OCEAN CITY INLET JETTY LIGHT...225 Ocean City Inlet Radiobeacon.................230 Ocean City Inlet Lighted Bell Buoy 2 ......240 Ocean City Research Buoy......................235 Ocean City Wreck Buoy WR2.................245 OCEAN PINES YACHT CLUB...........4925 Ocracoke Inlet......................................28895 Ocracoke Light ........................................660

Table 2-3 — Light List Index

Corrections to the Light List are made in the “Local Notice to Mariners” published by each Coast Guard district. These notices are essential for all navigators to keep their charts and Light List, current.