The shape of a cardinal mark is not important, but in
the case of a buoy, it will be a pillar or a spar.
When lighted, a cardinal mark exhibits a white
light. The characteristics are based on a group of quick
(Qk) or very quick (VQk) flashes. These flashes
distinguish it as a cardinal mark and indicate its
quadrant. The distinguishing QK or VQK flashes are as
East--three flashes in a group
Figure 6-24.--IALA Maritime Buoyage System, isolated
South--six flashes in a group followed by a long
The extent of the surrounding navigable water is not
West--nine flashes in a group
important. The isolated danger mark can, for example,
indicate either a shoal that is well offshore of an islet
As a memory aid, associate the number of flashes in
separated by a narrow channel from the coast.
each group with a clock face (3 o'clock--east, 6
o'clock--south, and 9 o'clock--west).
A black double-sphere topmark is, by day, the most
important feature of an isolated danger mark.
The long flash immediately following the group of
Whenever practical, this topmark will be carried with
flashes of a south cardinal mark is to ensure that its six
the spheres as large as possible, mounted vertically, and
flashes cannot be mistaken for three or nine.
Quick flashing lights flash at a rate of 50 to 79
The isolated danger mark is painted black, with one
flashes per minute. Very quick flashing lights flash at a
or more red horizontal bands. Its shape is not
rate of 80 to 159 flashes per minute. The two rates of
significant, but if the mark is a buoy, it will be a pillar or
flashing are used in situations that might cause
confusion for mariners. For example, suppose two
north buoys are placed near enough to each other that
If the danger mark is a spar buoy and is lighted, it
they might be mistaken for one another. In this case, one
will have a white flashing light showing a group of two
buoy would be set for quick flashing, while the other
flashes. The association of two flashes and two spheres
would be set for very quick flashing.
in the topmark may be a help in remembering these
ISOLATED DANGER MARKS
SAFE WATER MARKS
moored above, an isolated danger of limited extent. The
there is navigable water all around the mark. Such a
isolated danger mark has navigable water all around it.
Figure 6-25.--IALA Maritime Buoyage System, safe water marks.