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Judging distance
Accurate navigation also relies on the ability to correctly judge distance. The
best way to do this is to time your swimming pace or count your fin cycles.
A single fin cycle is completed every time the left foot kicks downward.
Determine how many cycles it takes you to swim a fixed distance such as
100 feet. Use a line that is precisely 100 feet in length and lay it straight
along the bottom. Swim the length of the line using your normal swim pace
and count each fin cycle. Repeat the swim four or five times and average the
different counts. Note that your pace at depth is likely different from your
pace on the surface.
Practice, Practice
You need lots of practice to become a good compass navigator. Dry land
practice is better than nothing, but to really master the art of underwater
navigation you need to go diving, preferably in an area with minimal
current. Practice choosing a point on the surface and trying to navigate
to that point underwater. Once you have that down, try swimming
back to where you started without surfacing. As a rule of thumb, a good
navigator can swim 300 feet out and 300 feet back and arrive within 15
feet of where he started.
When you are ready for the big leagues, try swimming right-hand
squares: Pick a heading and swim 100 feet, add 90° to the heading and swim
100 more feet in the new direction. Repeat this process twice more, and you
should arrive back where you started. If you get a number higher than 360°
at any point in your calculations, simply subtract 360° to get the heading you
should use. To complete a left square, use the same procedure, but subtract
90° at each turn. If you really want to go for mastery, try swimming triangles
by adding or subtracting 120° at each turn. Although you will probably never
enjoy doing every dive while watching nothing but your compass, these
skills provide an excellent foundation for practical navigation.
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WINTER 2012
digital compasses use a magnetometer
to detect the earth’s magnetic field.
silver
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