There area a wide veriety of non-lighted short range aids that navigatotors can use for course plotting and position fixing. Some of these aids use a later a system for detailed identification that can be a big help to navigation if you know what your looking at.

Lighthouses most often have no lateral significance and show no lateral markings. They usually exhibit a white light.

Occasionally, lighthouses use sectored lights to mark shoals or warn of other dangers. Lights so equipped show one color from most directions and a different color or colors over defined arcs as indicated on the chart.

Large navigational buoys (LNBs) were developed to replace lightships and were placed at points where it's impractical to build lighthouses. The unmanned LNBs were 40 feet in diameter with light towers approximately 40 feet above the water. These have largely been replaced either with ordinary buoys or Exposed Location Buoys (ELBs), which are somewhat larger than ordinary buoys but have the same markings.

Seasonal aids to navigation are placed into service or changed at specified times of the year. The dates shown in the Light List are approximate and may vary due to adverse weather or other conditions.

img10598Ranges are nonlateral aids that comprise pairs of aids that you can line up to assist you in maintaining a safe course. You must consult the chart when using ranges to determine if the range marks the centerline of the navigable channel and also what section of the range may be safely traversed. Ranges display rectangular dayboards of various colors and are generally lighted. (See Fig. 1, 2,.) When lighted, ranges may display lights of any color; in most cases, the front light is quick flashing and the rear light is isophase.

Sound signal is a generic term used to describe devices that produce an audible signal designed to assist you in fog or other periods of reduced visibility. These devices can be activated manually, remotely, or by a fog detector. Where a fog detector is used, there may be a delay in the automatic activation of the signal. Also, fog detectors may not detect patchy fog.

Sound signals are distinguished by their tone and phase characteristics. Tones vary with the devices producing the sound; for example, diaphones, diaphragm horns, sirens, whistles, bells, and gongs.

Phase characteristics are defined by the signal's sound pattern-the number of blasts and silent periods per minute. Signals sounded from fixed structures generally produce a specific number of blasts and silent periods each minute. Buoy sound signals are generally activated by the motion of the sea and therefore do not emit a regular signal characteristic. It is common, in fact, for a buoy to produce no sound signal when seas are calm.

The Light List gives the characteristic of a sound signal. Assume that the signal only operates during times of fog, reduced visibility, or adverse weather unless it is specifically stated that it operates continuously, or the signal is a bell, gong, or whistle on a buoy.

An emergency sound signal is sounded at some locations when the main and standby signals are inoperative.

CAUTION: Don't rely on sound signals to determine your position. You can't accurately determine distance by sound level. Occasionally, even nearby sound signals may not be heard, especially when they're downwind of you. Signals may not be activated when fog is nearby but not right at the location of the signal.

Variations To The U.S. System


Intracoastal Waterway aids to navigation: The Intracoastal Waterway runs parallel to the Atlantic and Gulf coasts from Manasquan Inlet, New Jersey, to the Mexican border. Aids in these waters have some yellow marking on them. Otherwise, their coloring and numbering follow the same system as other U.S. waters. The special Waterway markings consist of a yellow square or yellow triangle and indicate which side the aid should be passed when following the conventional direction of buoyage. The yellow square indicates that the aid to navigation should be kept on the left side; the yellow triangle indicates that the aid should be kept on the right side.

NOTE: The conventional direction of buoyage in the Intracoastal Waterway is generally southerly along the Atlantic coast and westerly along the Gulf coast.

The Western Rivers System— a variation of the standard U.S. Aids to Navigation System described in the preceding sections — is employed on the Mississippi River and its tributaries above Baton Rouge, Louisiana, and on certain other rivers that flow toward the Gulf of Mexico. The Western Rivers System varies from the standard U.S. system as follows:
    1. Aids to navigation are not always numbered.2. Any numbers on aids don't have lateral significance, but rather indicate mileage from a fixed point (normally the river mouth).

    3. Diamond-shaped crossing dayboards, red or green as appropriate, are used to indicate where the river channel crosses from one bank to the other.

    4. Lights on green aids to navigation show a single-flash characteristic, which may be green or white.

    5. Lights on red aids show a group-flash characteristic, which may be red or white.

    6. Isolated danger marks are not used.

Uniform State Waterway Marking System (USWMS): This system was developed in 1966 to provide an easily understood system for operators of small boats. Although designed for lakes and other inland waterways that are not portrayed on nautical charts, the USWMS is used on other waters as well. It supplements the existing federal marking system and is generally compatible with it.

The conventional direction of buoyage is upstream, or toward the head of navigation.

The USWMS varies from the standard U.S. system as follows:

  1. The color black is used instead of green.

  2. Three aids to navigation reflect cardinal significance:

    1. A white buoy with a red top represents an obstruction and should be passed to the south or west.

    2. A white buoy with a black top represents an obstruction and should be passed to the north or east.

    3. A red-and-white vertically striped buoy indicates that an obstruction exists between that buoy and the nearest shore.



  3. Mooring buoys are white buoys with a horizontal blue band midway between the waterline and the top of the buoy. When lighted, this buoy generally shows a slow-flashing white light.


Bridge Markings


Bridges across navigable waters are generally marked with red, green, and/or white lights. Red lights mark piers and other bridge parts. Red lights on drawbridges show when they are in the closed position. Green lights on drawbridges show when they are in the open position. The location of these lights varies according to bridge structure.

Green lights are also used to mark the centerline of navigable channels through fixed bridges. If there are two or more channels through the bridge, the preferred channel is also marked by three white lights in a vertical line above the green light.

Red and green retro-reflective panels mark bridge piers and may be placed on bridges not required to display lights.

Main channels through bridges may be marked by lateral red and green lights and dayboards. Adjacent piers are marked with fixed yellow lights when the main channel is marked with lateral aids to navigation.

Centerlines of channels through fixed bridges may be marked with a safe-water mark and an occulting white light when lateral marks are used to mark main channels. The centerline of the navigable channel through the draw span of floating bridges may be marked with a special mark-a yellow diamond with yellow retro-reflective panels-and may exhibit a yellow light that displays a Morse code "B" ( - . . . ).

Clearance gauges may be installed that indicate vertical clearance. The gauges are located on the right channel pier or pier protective structure facing approaching vessels.

Drawbridges equipped with radiotelephones display a blue-and-white sign that indicates what VHF channels the bridge-tender monitors.

Electronic Aids to Navigation


Racons
Some aids to navigation are enhanced by the use of RAdar beaCONS (racons). Racons, when triggered by pulses from your vessel's radar, transmit a coded reply to your radar. This identifies the racon station with a series of dots and dashes that emanate from the racon and appear on your radar screen. This display indicates the approximate range and bearing to the racon. Although racons may be used on both laterally significant and nonlaterally significant aids, the racon signal itself serves for identification purposes only and carries no lateral significance. Racons are also placed on bridges to mark the point of best passage.

All racons operate in the marine radar X-band from 9,300 to 9,500 MHz. Some frequency-agile racons also operate in the 2,900 to 3,000 MHz marine radar S-band.

Racons have a typical output of 100 to 300 milliwatts and so are short-range aids. Reception varies from a nominal range of six to eight nautical miles when mounted on a buoy, to as much as 17 nautical miles for a racon with a directional antenna mounted at a height of 50 feet on a fixed structure. These nominal ranges are a guide; actual ranges vary with many factors.

The beginning of the racon presentation appears on your radar screen about 50 yards beyond the racon position and persists for a number of revolutions of the radar antenna that depends on its rotation rate.

Distance to the racon can be measured to the point at which the racon flash begins, but the figure obtained is greater than your ship's distance from the racon. This is due to the slight response delay in the racon apparatus.

Radar operators may notice some broadening or spoking of the racon presentation when their vessel approaches close to the source of the racon. You can minimize this effect by adjusting the IF gain or sweep gain of your radar. If desired, you can virtually eliminate the racon presentation by operating the FTC (fast time constant) controls of your radar.

Radar Reflectors
Many aids to navigation incorporate special fixtures that enhance the reflection of radar energy. These radar reflectors help radar-equipped vessels to detect buoys and beacons. They do not, however, positively identify a radar target as an aid to navigation.

The Canadian Aids To Navigation System


To augment this brief discussion of the Canadian system, consult the Canadian coast pilots and small-craft guides. The Canadian Coast Guard publishes a book titled The Canadian Aids to Navigation System. (See Fig. 3.)

Canada uses the same IALA Region B system used in the United States in a combined lateral and cardinal system. The shape, color, and light characteristics all indicate the function of the aid to navigation.

In general, the "red right returning" rule applies. In addition, the system of cardinal marks indicates the relative position of obstructions. The cardinal buoys have double cone topmarks.

Canada also has special-purpose buoys that are usually similar to U.S. buoys designed for the same purpose. Daymarks include red triangles and green squares somewhat similar to marks used in the U.S. Intracoastal Waterway.

Canada uses the metric system, and lighthouse heights are given in meters rather than feet. Ranges of lights are still listed in nautical miles.