علم و هنر هدایت کشتی(اخبار روز دریایی) - علائم کمک ناوبری
هنرستان علوم و فنون دریایی,رشته ناوبری,محمد دلفروز عبدالملکی
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Navigation aids

Navigation aids are special structures like lighthouses, lightships, beacons, buoys, etc that are used to enhance safety by providing more opportunities to obtain LOPs.

These lights and marks are prescribed across the world by the International Association of Lighthouse Authorities (IALA). In 1977 this IALA endorsed two maritime buoyage systems putting an end to the 30 odd systems existing at that time. Region A (IALA A) covers all of Europe and most of the rest of the world whereas region B (IALA B) covers only the America's, Japan, the Philippines and Korea. Fortunately, the differences between these two systems are few. The most striking difference is the direction of buoyage (see Lateral buoys below). All marks within the IALA system are distinguished by:

  • Shape
  • Colour
  • Top mark
  • Light

Light Identification


During daytime identification of navigation aids is accomplished by observing: location, shape, colour scheme, auxiliary features (sound signals, RACON(responds to special signals)."); }" src="http://www.sailingissues.com/i7smal.gif" />, RCRadio beacon Circular."); }" src="http://www.sailingissues.com/i7smal.gif" />, etc) or markings (name, number, etc).

During the night, we use the features of the navigation aid's light to both identify it and ascertain its purpose. There are three features to describe the light:

  • Colour: Either white, red, green or yellow. If no colour is stated in the chart, default is white.
  • Period: The time in seconds needed for one complete cycle of changes. period of light   The arrow indicates the 10 second period of this flashing light 'Fl(3) 10 s'.
  • Phase characteristic: The particular pattern of changes within one complete cycle (hence, within one period). Below are the most common types:
  • Fixed (F)
    Fixed   This light shines with an unblinking and steady intensity and is always on. In this example a yellow fixed light is shown.
  • Flashing (Fl):
    Flashing   The duration of the light is always less than the duration of the darkness. The frequency does not exceed 30 times per minute.
  • Quick Flashing (Q):
    Quick Flashing   Again, the duration of quick flash is less than the darkness. The frequency is at least 60 times per minute.
  • Very Quick Flashing (VQ):
    Very Quick Flashing   Also here, the duration of very quick flash is less than the darkness. The frequency is at least 100 times per minute.
  • Interrupted Quick Flashing (IQ):
    Interrupted Quick Flashing   Like Quick Flashing with one moment of darkness in one period.
  • Isophase (Iso):
    Isophase or Equal Interval (E int).   This Light has equal duration between light and darkness. A period consists of both a light and a dark interval. Also called Equal Interval (E Int).
  • Group Flashing (Gp Fl(x+x)):
    Group flash (2+3)   This is actually a combination of two patterns in one period. In this example the first 2 flashes followed by the pattern of 3 flashes result in 'Gp Fl(2+3)'.
  • Occulting (Occ):
    Occulting   Occulting is the opposite of flashing, the light is more on then off.
  • Alternating (AL):
    Alternating White Green   An alternating light changes colour. This special purpose light is typically used for special applications requiring the exercise of great caution. In this example ALT.WG is shown, alternating between green and white.
  • Morse "U" (Mo (U)):
    Morse code: U   This light shows two flashes and a longflash, which is equivalent to the letter "U" in Morse code.
  • Long-Flashing (LFL):
    Long Flash   This light has one long flash in a period. A long flash is at least 2 seconds long.
Let's look at some examples using colour, period and phase characteristics. The arrows mark the periods:
  •   Fl (4) 8 s
  •   Oc (2+3) 10 s
  •   Iso G 4 s

All lighted navigation aids are either major or minor lights, where major lights are used for key navigational points along seacoasts, channels and harbour and river entrances. These lights are normally placed in lightships, lighthouses and other permanently installed structures, providing both high intensity and high reliability of the lights. Major lights are then subdivided in primary lights (very strong, long range lights used for the purpose of making landfalls or coastal passages) and secondary lights (shorter range lights found for example at harbour and river entrances). Important details of (especially) primary lights can be found in a reference called the Light List where information (about pedestals etc.) can be found which is not included in the chart.
Minor lights on the other hand are likely to be found within harbours, along channels and rivers. These have a low to moderate intensity and sometimes mark isolated dangers.

Five types of navigation buoys:

  • Lateral
  • Cardinal
  • Isolated danger
  • Safe water
  • special


Lateral Buoys and Marks


The location of lateral buoys defines the borders of channels and indicates the direction. Under IALA A red buoys mark the port side of the channel when returning from sea, whereas under IALA B green buoys mark the port side of the channel when sailing towards land. Red buoys have even numeration plus red lights and green buoys have odd numeration plus green lights. Lateral lights can have any calm phase characteristic except FL (2+1).
Lateral red buoy.Lateral green buoy.

Preferred channel to starboard: keep buoy to port (IALA A). Generally, when two channels meet one will be designated the preferred channel (i.e. most important channel). The buoy depicted on the right indicates the preferred channel to starboardThe other channel requires a green buoy there."); }" src="http://www.sailingissues.com/i7.gif" /> under IALA A. The light phase characteristic is R FL (2+1): Red buoy indicating a preferred channel to port (in USA, Japan..

Preferred channel to port: keep buoy to starboard (IALA A).The buoy depicted on the left indicates the preferred channel to portThe other channel requires a red buoy there."); }" src="http://www.sailingissues.com/i7.gif" /> under IALA A. These buoys are marked with the numerations of both channels. The light phase characteristic is G FL (2+1):
Gree buoy indicating a preferred channel to starboard (in USA, Japan).


Cardinal Buoys


The four cardinal buoys indicate the safe side of a danger with an approximate bearing. For example, the West cardinal buoy has safe water on its West and the danger on its East side. Notice the 'clockwise' resemblance of the light phase characteristics. The topmarks consist of two black triangles placed in accordance with the black/yellow scheme of the buoy. When a new obstacle (not yet shown on charts) needs to be marked, two cardinal buoys will be used to indicate this 'uncharted' danger. The cardinal system is identical in both the IALA A and IALA B buoyage systems.

Cardinal buoys around a selection of dangers.


Marks indicating Isolated dangers


Marks indicating isolated dangers.This type of buoy indicates the position of an isolated danger, contrary to cardinal buoys which indicate a direction away from the danger. The light (when present) consists of a white group flash: Fl(2).
Marking of isolated dangers


Marks indicating Safe water


Marks indicating safe water. Notice that whereas most horizontal striping 'spells danger', this safe water buoy is vertically striped. These marks are for example seaward of all other buoys (lateral and cardinal) and can be used to make landfall. Lights are usually calm and white.


Special Buoys and Marks


Marks used for special indication.
We saved these buoys for last since they have not an actual navigation purpose. Most of the time these yellow buoys indicate areas used by navies or pipelines or surfing.




It is important to know at what distance (range) we may see a certain light, and when we can expect to lose sight of it, especially when making landfall. This range can be defined in several ways:

  • Charted or Nominal Range: The nominal range is indicated in the chart next to the light or can be found in the Light List. This is the maximum distance at which a light may be seen at night based upon intensity and 10 nautical miles of visibility.
+ نوشته شده در  جمعه بیست و چهارم آبان 1387ساعت 16:39  توسط محمد دلفروز |