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navigation - page 8

6.8 Lights and Buoys


By night, some (but not all) navigational aids are lit. So that you can tell then difference between them they all have particular characterisics It is only by referencing a chart at you will be able to identify a lights exact purpose however.


Characteristic | Short-hand | Notes

Fixed | F | Always on

Flashing | Fl | Flashes once in a set time.

Group Flashing | Fl(3) | Flashes a set number of times in a set time (number of flashes in brackets).

Isophase | Iso | On for the same time as off.

Occulting | Oc | On most of the time and then flashes off.

Morse | Mo(A) | Morse letter shown in brackets.

Cycle period | 10s | 10 seconds

The high of the light | 15m | 15 meters

The range in which the light is visible | 10M | 10 nautical miles

Light can come in a number of different colours but if not referred to the colour will be white. Otherwise the following codes are used:

R – Red
G – Green
Y – Yellow
Bl – Blue


Lights will repeat there characterisics in a set time or period. This is shown after the other light details ie. 15s means it repeats every 15 seconds.

Some examples:

Short-hand | Meaning

Fl.R 5s | Flashing red once every 5 seconds

Fl(4) 15s | Flashing white four times every 15 seconds

Iso 10s | White light on for 5 seconds off for 5 seconds

Oc 12s | White light flashing off once every 12 seconds

Mo(U) 20s | White light flashing Morse code U once every 20 seconds

Sectored Lights

Some lights are sectored, that is to say they appear as a different colour and/or timing dependent on which way you appoach it.


The divisions between these different sectors as shown on the chart as dotted lines coming out from the lights position. The colour is then indicated on the arcs drawn between these lines. 

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Example 1: Light "Ak. Tourlos"


A group of 3 flashes.

White colour (it doesn't write the colour so it's white).

Repeat every 6 seconds.

The light is 28 metres above the chart datum.

It is visible for 5 nautical miles.

Example 2: Light "Ag.Marina"


1 Flashing.

Green colour.

Repeat every 2 seconds.

The light is 5 metres above the chart datum.

It is visible for 3 nautical miles.

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Example 1: Light "Ak.Aimilianos"


1 Flashing

White and Red colour

Repeat every 10 seconds

The light is 7 metres above the chart datum

It is visible for 8 nautical miles (white), 6 nautical miles (red). 

Example 2: Light "Steno Petassi"


A group of 2 flashes

White and Red colour

Repeat every 12 seconds

The light is 7 metres above the chart datum

It is visible for 8 nautical miles (white), 4 nautical miles (red). 


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

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 38 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).

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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.


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).

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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.

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Special Buoys and Marks

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.

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Port lighting

When entering a port or when travelling upstream or away from the sea (for channels):

  • keep port (red) marks on your port-hand side (left).

  • keep starboard (green) marks on your starboard hand side (right).

When travelling out of a port or when downstream or towards the sea (for channels):

  • keep port (red) marks on your starboard-hand side (right).

  • keep starboard (green) marks on your port-hand side (left).

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