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FIELD-EXPEDIENT DIRECTION FINDING
In a survival
situation, you will be extremely fortunate if
you happen to have a map and compass. If you do have
these two pieces of equipment, you will most likely be able
to move toward help. If you are not proficient in using
a map and compass, you must take the steps to gain
this skill.
There are several methods by which you can determine
direction by using the sun and the stars. These methods,
however, will give you only a general direction. You can
come up with a more nearly true direction if you know the
terrain of the territory or country.
You must learn all you can about the terrain of the country
or territory to which you or your unit may be sent,
especially any prominent features or landmarks. This
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knowledge of the terrain together with using the methods
explained below will let you come up with fairly true directions
to help you navigate.
USING THE SUN
AND SHADOWS
The earth’s relationship to the sun can help you to determine
direction
on earth. The sun always rises in the east and sets in the west,
but not
exactly due east or due west. There is also some seasonal
variation. In
the northern hemisphere, the sun will be due south when at its
highest
point in the sky, or when an object casts no appreciable shadow.
In the
southern hemisphere, this same noonday sun will mark due north.
In the
northern hemisphere, shadows will move clockwise. Shadows will
move
counterclockwise in the southern hemisphere. With practice, you
can use
shadows to determine both direction and time of day. The shadow
methods
used for direction finding are the shadow-tip and watch methods.
Shadow-Tip Methods
In the first shadow-tip method, find a straight stick 1 meter
long, and a
level spot free of brush on which the stick will cast a definite
shadow.
This method is simple and accurate and consists of four steps:
Step 1. Place the stick or branch into the ground at a level
spot
where it will east a distinctive shadow. Mark the shadow’s tip
with
a stone, twig, or other means. This first shadow mark is always
west —everywhere on earth.
Step 2. Wait 10 to 15 minutes until the shadow tip moves a few
centimeters. Mark the shadow tip’s new position in the same way
as the first.
Step 3. Draw a straight line through the two marks to obtain an
approximate east-west line.
Step 4. Stand with the first mark (west) to your left and the
second
mark to your right-you are now facing north. This fact is true
everywhere on earth.
An alternate method is more accurate but requires more time. Set
up
your shadow stick and mark the first shadow in the morning. Use
a piece
of string to draw a clean arc through this mark and around the
stick. At
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midday, the shadow will shrink and disappear. In the afternoon,
it will
lengthen again and at the point where it touches the arc, make a
second
mark. Draw a line through the two marks to get an accurate
east-west
line (see Figure
1).
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The Watch Method
You can also determine direction using a common or analog
watch—one
that has hands. The direction will be accurate if you are using
true local
time, without any changes for daylight savings time. Remember,
the further
you are from the equator, the more accurate this method will be.
If
you only have a digital watch, you can overcome this obstacle.
Quickly
draw a watch on a circle of paper with the correct time on it
and use it
to determine your direction at that time.
In the northern hemisphere, hold the watch horizontal and point
the
hour hand at the sun. Bisect the angle between the hour hand and
the
12 o’clock mark to get the north-south line (Figure
2). If
there is any
doubt as to which end of the line is north, remember that the
sun rises
in the east, sets in the west, and is due south at noon. The sun
is in the
east before noon and in the west after noon.
Note: If your watch is set on daylight savings time, use the
midway point
between the hour hand and 1 o'clock to determine the north-south
line.
In the southern hemisphere, point the watch’s 12 o’clock mark
toward
the sun and a midpoint halfway between 12 and the hour hand will
give
you the north-south line (Figure
2).
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USING THE MOON
Because the moon has no light of its own, we can only see it
when it
reflects the sun’s light. As it orbits the earth on its 28-day
circuit, the
shape of the reflected light varies according to its position.
We say there
is a new moon or no moon when it is on the opposite side of the
earth
from the sun. Then, as it moves away from the earth’s shadow, it
begins
to reflect light from its right side and waxes to become a full
moon before
waning, or losing shape, to appear as a sliver on the left side.
You
can use this information to identify direction.
If the moon rises before the sun has set, the illuminated side
will be the
west. If the moon rises after midnight, the illuminated side
will be the
east. This obvious discovery provides us with a rough east-west
reference
during the night.
USING THE STARS
Your location in the Northern or Southern Hemisphere determines
which constellation you use to determine your north or south
direction.
The Northern Sky
The main constellations to learn are the Ursa Major, also known
as the
Big Dipper or the Plow, and Cassiopeia (Figure
3). Neither of
these
constellations ever sets. They are always visible on a clear
night. Use
them to locate Polaris, also known as the polestar or the North
Star.
The North Star forms part of the Little Dipper handle and can be
confused
with the Big Dipper. Prevent confusion by using both the Big
Dipper and Cassiopeia together. The Big Dipper and Cassiopeia
are
always directly opposite each. other and rotate counterclockwise
around
Polaris, with Polaris in the center. The Big Dipper is a seven
star constellation
in the shape of a dipper. The two stars forming the outer lip
of this dipper are the “pointer stars” because they point to the
North
Star. Mentally draw a line from the outer bottom star to the
outer top
star of the Big Dipper’s bucket. Extend this line about five
times the
distance between the pointer stars. You will find the North Star
along
this line.
Cassiopeia has five stars that form a shape like a “W” on its
side. The
North Star is straight out from Cassiopeia’s center star.
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After locating the North Star, locate the North Pole or true
north by
drawing an imaginary line directly to the earth.
The Southern Sky
Because there is no star bright enough to be easily recognized
near the
south celestial pole, a constellation known as the Southern
Cross is used
as a signpost to the South (Figure
4). The Southern Cross or
Crux
has five stars. Its four brightest stars form a cross that tilts
to one side.
The two stars that make up the cross's long axis are the pointer
stars.
To determine south, imagine a distance five times the distance
between
These stars and the point where this imaginary line ends is in
the general
direction of south. Look down to the horizon from this imaginary
point
and select a landmark to steer by. In a static survival
situation, you can
fix this location in daylight if you drive stakes in the ground
at night to
point the way.
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MAKING IMPROVISED COMPASSES
You can construct improvised compasses using a piece of ferrous
metal
that can be needle shaped or a flat double-edged razor blade and
a piece
of nonmetallic string or long hair from which to suspend it. You
can
magnetize or polarize the metal by slowly stroking it in one
direction
on a piece of silk or carefully through your hair using
deliberate strokes.
You can also polarize metal by stroking it repeatedly at one end
with a
magnet. Always rub in one direction only. If you have a battery
and
some electric wire, you can polarize the metal electrically. The
wire
should be insulated. If not insulated, wrap the metal object in
a single,
thin strip of paper to prevent contact. The battery must be a
minimum
of 2 volts. Form a coil with the electric wire and touch its
ends to the
battery’s terminals. Repeatedly insert one end of the metal
object in
and out of the coil. The needle will become an electromagnet.
When
suspended from a piece of nonmetallic string, or floated on a
small piece
of wood in water, it will align itself with a north-south line.
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You can construct a more elaborate improvised compass using a
sewing
needle or thin metallic object, a nonmetallic container (for
example, a
plastic dip container), its lid with the center cut out and
waterproofed,
and the silver tip from a pen. To construct this compass, take
an ordinary
sewing needle and break in half. One half will form your
direction
pointer and the other will act as the pivot point. Push the
portion used
as the pivot point through the bottom center of your container;
this portion
should be flush on the bottom and not interfere with the lid.
Attach
the center of the other portion (the pointer) of the needle on
the pen’s
silver tip using glue, tree sap, or melted plastic. Magnetize
one end of
the pointer and rest it on the pivot point.
OTHER MEANS
OF DETERMINING DIRECTION
The old saying about using moss on a tree to indicate north is
not
accurate because moss grows completely around some trees.
Actually,
growth is more lush on the side of the tree facing the south in
the
Northern Hemisphere and vice versa in the Southern Hemisphere.
If
there are several felled trees around for comparison, look at
the stumps.
Growth is more vigorous on the side toward the equator and the
tree
growth rings will be more widely spaced. On the other hand, the
tree
growth rings will be closer together on the side toward the
poles.
Wind direction may be helpful in some instances where there are
prevailing
directions and you know what they are.
Recognizing the differences between vegetation and moisture
patterns
on north- and south-facing slopes can aid in determining
direction. In
the northern hemisphere, north-facing slopes receive less sun
than
south-facing slopes and are therefore cooler and damper. In the
summer,
north-facing slopes retain patches of snow. In the winter, the
trees
and open areas on south-facing slopes are the first to lose
their snow,
and ground snowpack is shallower.
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