avoiding collision by eye or radar 133
Make sure you take the bearing to
the same part of the vessel (or same
light) each time.
A series of drift bearings taken
over a few minutes will show the
vessel’s bearing drift relative to your
boat. If the vessel drift s to the right,
it is said to have right bearing drift. If
the vessel drift s left it is said to have
left bearing drift. If the bearings show
no change over time, the vessel has a
steady bearing drift , which means you
have a high risk of collision.
You must also observe the rate
of drift. Th is drift rate is not a math-
ematical formula, but an observa-
tion. If the bearings change slowly,
the vessel has a slow drift rate. If the
bearings change rapidly, it has a fast
drift rate. Th e faster the drift rate, the
lower the risk of collision. Use drift
bearings, bearing drift , and drift rate
together to decide whether you must
maneuver to avoid a collision.
One of three situations always
exists between vessels:
Meeting: Two vessels are moving
toward each other, end to end.
Th is includes vessels bow to bow,
bow to stern, or stern to stern.
Crossing: One vessel moves against
the other. Vessels cross from left
to right or from right to left.
Overtaking: A faster vessel is coming
up from behind a slower vessel.
In a busy channel, harmless meetings
between vessels can quickly change
to dangerous crossing situations. For
this reason, you must maintain a
visual watch on any vessel until it no
longer presents a risk of collision.
Download a Free Copy of
the Navigation Rules
Add a copy of the Navigation Rules
for International and U.S. Inland
Waters to your onboard library. This
book has but one purpose: to advise
mariners on how to prevent collisions
on any body of water on the planet.
Download a free copy from the U.S.
Coast Guard’s Navigation Center at
http://www.navcen.uscg.gov/mwv/
navrules/download.htm.
Do this now, before reading further,
and use the navigation rules to help
you understand the concepts we
discuss. Always keep a copy onboard
your boat. (In fact, certain commercial
vessels are required to keep a copy of
the rules on board.) Before long, your
copy of the rules will become one of the
most highlighted, dog-eared nautical
books onboard! And you’ll fi nd yourself
referring to it time and again for advice
on avoiding collision, vessel lighting,
fog, and distress signals.
Note from the publisher: among
the commercially published editions
of the navigation rules is The One-
Minute Guide to the Nautical Rules
of the Road (by Charlie Wing; 0-07-
147923-6), which includes illustrations
and interpretations along with
the precise language of the rules,
and which also highlights the few
differences between the U.S. Inland
Rules and the International Rules
that apply in U.S. coastal waters and
around the world. You can also fi nd
a condensed version of the rules in
Charlie Wing’s Captain’s Quick Guide:
Rules of the Road and Running Light
Patterns, 0-07-142369-9.