By day, topmarks are the most important features
of cardinal marks. The arrangement of the cones must
be memorized. For north, the points of the cones is up;
and for south, the points of the cones is down. An aid
to help you memorize the west topmark is that it
resembles a wineglass. Cardinal marks carry
topmarks, whenever practical, with cones as large as
possible and clearly separated.
Black and yellow horizontal bands are used to
color cardinal marks. The position of the black band,
or bands, is related to the point of the black topmarks.
The black and yellow horizontal bands are used as
NorthBlack bands above yellow bands
SouthBlack bands below yellow bands
WestBlack band with yellow bands above and
EastBlack bands above and below yellow
The shape of a cardinal mark is not important; but
in the case of a buoy, it will be pillar or spar.
When lighted, a cardinal mark exhibits a white
An isolated danger mark (fig. 9-16) is erected on,
light. The characteristics are based on a group of quick
or moored above, an isolated danger of limited extent.
(Q) or very quick (VQ) flashes, which distinguishes it
An isolated danger mark has navigable water all
as a cardinal mark and indicates its quadrant. The
around it. The extent of the surrounding navigable
distinguishing quick or very quick flashes are as
water is not important. The isolated danger mark can,
for example, indicate either a shoal that is well
NorthVery quick flashing (VQ) or quick
EastVery quick flashing every 5 seconds (VQ
(3) 5s) or quick flashing every 10 seconds (Q (3) 10s)
SouthVery quick flashes followed by a long
flash every 10 seconds (VQ FL (6) + LFl 10s) or quick
flashing followed by a long flash every 15 seconds
(Q (6) + LFl 15s)
WestVery quick flashing light every 10 seconds
(VQ (9) 10s) or quick flashing every 15 seconds
(Q (9) 15s)
As a memory aid, associate the number of flashes
in each group with a clock face (3 o'clock, east; 6
o'clock, south; and 9 o'clock, west).
The long flash immediately following the group
of flashes from a south cardinal mark is to ensure that
its six flashes cannot be mistaken for three or nine.
Quick flashing lights flash at a rate of either 50 or
60 flashes per minute. Very quick flashing lights flash
at a rate of either 100 or 120 flashes per minute. It is
necessary to have a choice of quick or very quick
flashing light to avoid confusion. Two north buoys
that are placed near enough to each other to be
mistaken is one example where the quick flashing or
very quick flashing lights would be needed.
ISOLATED DANGER MARKS
Figure 9-16.IALA Maritime Buoyage System isolated danger marks.