Cardinal mark

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

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

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:

  • the direction of its two conical top-marks, which can both point up, indicating north; down, indicating south; towards each other, indicating west; or away from each other, indicating east
  • its distinctive pattern of black and yellow stripes, which follows the orientation of the cones - the black stripe is in the position pointed to by the cones (e.g. at the top for a north cardinal, in the middle for a west cardinal)
  • optionally, its distinctive sequence of flashing light, which consists of a sequence of quick or very quick flashes whose number gives the clockface position which corresponds to the direction of the cardinal (e.g. three for an east cardinal, nine for a west; north has continuous flashes, and south may be augmented with a long flash, to help distinguish it from a west in difficult conditions)
Summary of mark characteristics[1]
CharacteristicNorthSouthEastWest
Topmark Both cones point upwardsBoth cones point downwardsCones point away from each othercones point towards each other
Colour Black above yellowYellow above blackYellow horizontal band on a black bodyBlack horizontal band on a yellow body
Light (if fitted) Continuous flashes6 quick flashes + 1 long flash3 flashes9 flashes

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:

  • Indicate that the deepest water is an area on the named side of the mark
  • Indicate the safe side on which to pass a danger
  • Draw attention to a feature in a channel, such as a bend, junction, branch, or end of a shoal
  • Draw attention to a new danger such as a grounded ship. In such cases two equal marks are often placed together to indicate that it's a newly marked danger and is not yet printed in official charts.

Other uses:

  • Sometimes a Cardinal Mark can be used instead of a Special mark to indicate a spoil ground, or an outfall pipe for example. A few examples can be seen on the South Coast of England and in Northern France.

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 topmarks for east and west "follow the Sun"—the top cone points in the direction in which the Sun appears to move (rising for an east mark or setting for a west mark), while the bottom cone points in the direction in which its reflection on the ocean surface appears to move. That is, the Sun and its reflection move away from each other on rising and toward each other on setting.
  • East looks like an Easter egg. The western mark has a pinched waist: "Western women have wasp waists".[2]
  • East looks like a classical letter E/epsilon. The western mark looks like a "W" on its side, or "West winds wool" (looks like a bobbin)[3]
  • East is larger around the middle: "Equatorially enlarged". West is a woman's waist.[4]

The colours can be remembered this way: Black has no colour and a point has no size, while yellow has lots of colour and the base of the cone is its largest part.

Examples
  • Knoll North Cardinal
  • The 'East Bramble' East Cardinal Mark helps the Stavros S Niarchos navigate safely in the Solent, August 2008
  • All four types of cardinal mark used in Nanaimo Harbour to warn of an old concrete base.
  • A light buoying cardinal mark in pressure of ice in front of Helsinki, Finland in winter. Notice that topmark is not used on a buoy that is subjected to ripping by movements of ice.
gollark: *is disinclined to*
gollark: Well, it's more metro, not exactly simpler.
gollark: And would it be easier in Windows? It generally swaps the terminal for cryptic registry entries, dubious third-party software, and mysterious settings buried deep in control panel.
gollark: What stuff did you *need* to configure using a terminal?
gollark: GUI ones I mean.

See also

References
  1. IALA 2010, p. 14.
  2. Noice 2013, p. 130.
  3. Cunliffe 2016, p. 34.
  4. RYA 1985, plates between pp 72 and 73.

Citations
  • Cunliffe, Tom (2016) [2002], The complete day skipper (fifth ed.), Adlard Coles nautical (an imprint of Bloomsbury), ISBN 978-1-4729-2416-2
  • Cardinal Marks (PDF), IALA, archived from the original (PDF) on 2007-12-14, retrieved 2010-06-01
  • Maritime buoyage system and other aids to navigation (PDF), IALA (International association of maritime aids to navigation and lighthouse authorities), 2010, retrieved 11 August 2019
  • Noice, Alison (2013) [2007], Day skipper for sail & power (second ed.), Adlard Coles nautical (an imprint of Bloomsbury), ISBN 978-1-4081-9310-5
  • Navigation, an RYA manual (second ed.), Newton Abbot: David & Charles, 1985 [1981], ISBN 0-7153-8631-X
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