IALA Cardinal Marks

Cardinal Marks are primarily used to indicate the position of a hazard and the direction of safe water.

Cardinal Marks are named after the (4) main cardinal points of the compass (North Cardinal Mark, South Cardinal Mark, East . . . (Ok, so you get the idea.) The attribute that makes the Cardinal Mark so useful to the mariner is that there is no dependency on the position of or the direction of travel of an approaching vessel. The Cardinal Mark will always tell you where safe water lies and that will always be to the named side of the mark.

In the example shown below, the "East Cardinal Mark" indicates that safe water will be found to the east of the mark.

Likewise with the other marks, safe water is always found to the named side of the mark.

Cardinal Marks – Topmarks and Color Schemes

All Cardinal Marks are horizontally banded yellow and black and have black cone shaped topmarks. During daylight hours, the band colors, and topmarks are used to identify which cardinal mark you are observing.

• Topmarks are always black.
• North Cardinal Mark (both topmarks pointing up) Black band above yellow band.
• South Cardinal Mark (both topmarks pointing down) Black band below yellow band.
• East Cardinal Mark (topmarks pointing away from each other) Black band above and below yellow band.
• West Cardinal Mark (topmarks pointing towards each other) Black band between yellow bands.

A good memory aid to help keep the color scheme straight in your mind is by using the top marks to tell you where the black band/s are located in relation to the yellow band/s.

Cardinal Marks – Light Characteristics

When lighted, Cardinal Marks will:

• Only show white lights.
• Will always be either “Quick Flashing (Q)” or “Very Quick Flashing (VQ).”
• The cycle period will either be 5, 10, or 15 seconds.
• The phase characteristic is different for each of the Cardinal Marks to allow for their identification at night

The North Cardinal Mark will show a continuous “Q” or “VQ” white light.
The East Cardinal Mark will show a “Q(3) 10s” or “VQ(3) 5s” white light.
The South Cardinal Mark will show a “Q(6) + LFl 15s” or “VQ(6) + LFl 10s” white light.
The West Cardinal Mark will show a “Q(9) 15s” or “VQ(9) 10s” white light.

Quick Flashing (Q) is usually defined as a rate of 50 or 60 flashes per minute. Very Quick Flashing (VQ) is a rate of 100 or 120 flashes per minute.

Another memory aid to help easily remember and identify these lights at night, is to visualize the face of a clock with the cardinal marks at 12, 3, 6, and 9 and equate that to the flash count of the light.

Due to Cardinal Marks’ use of Quick Flashing and especially Very Quick Flashing lights, it often happens that some confusion can arise on the number of flashes observed. To help in preventing confusion between the Marks, a single Long Flash (L Fl) of 2 second duration is added to the South Cardinal Mark.

Cardinal Marks - Points to Remember

• Cardinal Marks are the same regardless if you are in IALA Region A or Region B.
• Are always colored with some combination of black and yellow horizontal bands.
• Always use some combination of black double cones for their topmark.
• Only show a white light if a lighted aid.
• A Cardinal Mark may also have safe water in other directions. A good example would be the “West Mark” above, it may also have deep water to the north and south of it, but by convention, the mariner will always know that there is good water to the west of the mark.
• For the U.S. boater who never ventures beyond their territorial waters, Cardinal Marks are seldom, if ever encountered. For the world cruiser however, you will eventually come across one. Be prepared!