Cardinal mark

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Diagram of cardinal marks as seen during the day, with their light patterns. The lights shown here are configured as "Quick". Cardinal Marks.gif
Diagram of cardinal marks as seen during the day, with their light patterns. The lights shown here are configured as "Quick".

A cardinal mark is a sea mark (a buoy or other floating or fixed structure) commonly used in maritime pilotage to indicate the position of a hazard and the direction of safe water.

Contents

Cardinal marks indicate the direction of safety as a cardinal (compass) direction (north, east, south or west) relative to the mark. This makes them meaningful regardless of the direction or position of the approaching vessel, in contrast to the (perhaps better-known) lateral mark system.

Characteristics

The characteristics and meanings of cardinal marks are as defined by the International Association of Lighthouse Authorities.

A cardinal mark indicates one of the four compass directions by: [1]

Summary of mark characteristics [1] [2]
CharacteristicNorthSouthEastWest
ShapePillar or sparPillar or sparPillar or sparPillar or spar
ColourBlack above yellowYellow above blackYellow horizontal band on a black bodyBlack horizontal band on a yellow body
Topmark

(always attached)



Both cones point upwards


Both cones point downwards


Cones point away from each other


Cones point towards each other
Light colour

(if light attached)

WhiteWhiteWhiteWhite
Light characteristic

(if light attached)

Continuous flashes at a rate of at least 50 per minute

Abbreviated as one of:

  • VQ W
  • Q W
6 quick flashes followed by 1 long flash, repeated every 10 or 15 seconds

Abbreviated as one of:

  • VQ(6) LFl W 10s
  • Q(6) LFl W 15s
3 flashes, repeated every 5 or 10 seconds

Abbreviated as one of:

  • VQ(3) W 5s
  • Q(3) W 10s
9 flashes, repeated every 10 or 15 seconds

Abbreviated as one of:

  • VQ(9) W 10s
  • Q(9) W 15s

Either a quick or a very quick sequence of light flashes may be used; the choice allows for two similar nearby marks to be uniquely identified by their lights.

A cardinal mark may be used to accomplish the following:

Other uses:

Mnemonics

The north and south topmarks are self-explanatory (both cones pointing up, or both pointing down). Remembering the east and west marks can be more of a problem.

The most natural way to distinguish the topmarks for east and west is to "follow the Sun"—the top cone indicates the direction the Sun would appear to move when visible in the part of the sky that corresponds to the mark's communicated direction, while the bottom cone indicates likewise for the Sun's reflection on a calm ocean surface. So when a topmark consists of two cones pointing away from each other, this should suggest the Sun moving away from its reflection on a calm ocean surface, which happens when the Sun rises, and a rising Sun is visible to the east. Likewise, a topmark with two cones pointing toward each other should suggest a setting Sun, which is visible to the west. [3]

Other mnemonics have been devised for the east and west marks in case the mnemonic that uses the Sun is difficult to grasp. For example:

The colours can be remembered this way: The two conical top-marks always point to black.

See also

References

  1. 1 2 "R1001 The IALA Maritime Buoyage System". International Association of Marine Aids to Navigation and Lighthouse Authorities. Retrieved 2025-07-09.
  2. 1 2 "R0110 – Rhythmic Characters of Lights on Aids to Navigation". International Association of Marine Aids to Navigation and Lighthouse Authorities. Retrieved 2025-07-09.
  3. Sanders 2018.
  4. Noice 2013, p. 130.
  5. Cunliffe 2016, p. 34.
  6. RYA 1985, plates between pp 72 and 73.

Citations