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Th e navigator’s job is a specialized one but not sacred. He or she should
never feel above explaining it to shipmates.
—John Rousmaniere, The Annapolis Book of SeamanshipWhat is the fastest way to predict when you will sight the cliff -top lighthouse
17 miles ahead? With our position in doubt, what three things must we know
before turning toward land? How can we use GPS to plot our position onto
a chart faster than ever before?
In Th is Chapter, You’ll Learn How To:
D Avoid dangers with a single bearing or range
D Pass a treacherous, rock-strewn reef without using a chart
D Turn the sides of your boat into powerful navigation tools
D Plot positions in under 5 seconds—using only a pencil!
D Reach any windward destination quickly and in complete safety
DR Plotting and the Boat-Trackline Connection
Even now, in the age of GPS, you need to back up all other forms of navigation
with basic dead reckoning (DR). DR navigation uses the three factors of time,
distance, and speed to estimate a boat’s movement from one point to another.
For instance, if you know your boatspeed and the distance you have to go,
you can determine the time of arrival, as we saw in Chapter 3. In Chapter 2
we prepared our charts with tracklines. You can use dead reckoning to plan
your trip before casting off. If you measure the trackline distance and predict your
speed, you will get a good idea of how much time it should take to reach your
destination.
A navigator uses similar techniques in a sailboat tacking upwind, though
often for shorter distances. For instance, you can measure the predicted length
of each tacking leg (distance), predict your speed on that leg (speed), and
then calculate the elapsed time to the next tack. As soon as the next tack is
made, the time is started again and the process repeated.
PILOTING
TIPS AND
TECHNIQUES
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