

How
do I use a map, compass, and altimeter?
Some
instructions never seems to make sense until you actually try to
do them. This FAQ is one of those things. Simply reading without
trying the exercise may be confusing.
A
map, compass, and altimeter can be used for two general uses.
One, to find where you are and two, to
determine where to go. Take the time to practice before
you need to use these skills. Practice often.
To find where you are:
Triangulation
Method: First, find two landmarks. It helps if they are
close to 90° from each other relative to your position.
Next, take a bearing for these landmarks.
Add or subtract the magnetic
declination. Plot these bearings on your
map. The point where the two bearings intersect is your
position. The same can be done with several landmarks for
more accuracy.
Altimeter Method: This method works best if you are on
a trail, ridgeline, or valley that contains a large section
that is all uphill or all downhill. It can also be used in
conjunction with the triangulation method to determine your
position more accurately. First, be sure that you altimeter
has been calibrated. Next, find the point
on your map where the trail, ridgeline, or valley intersects
the contour
line that most closely corresponds to your
altimeter reading.
To
determine where to go:
If
you are on a trail but you can not determine if you are
going in the right direction, a quick glance at the map and
compass should sort things out.
If
you are not on a trail, you will need a more precise
method of determining the correct direction of travel. First,
plot your desired course on your map to determine
your true compass heading. Then add or subtract the magnetic
declination. Now hold the compass at eye level and take
a bearing to determine which object on the horizon you
want to head for. Start walking toward that object until you
reach it or loose site of it. Repeat the process until you
reach your final destination.
Terms
and methods:
Taking a bearing:


Hold the compass in
your hand and turn yourself until the red
end of the compass needle (North)
coincides with the red arrow in the
bottom of the compass housing. The front
of the compass with the direction of
travel arrow is now pointing towards your
destination.
The reverse can be done to determine the
bearing based on a particular object. 



Using
a compass with a folding mirror is far
more accurate. Follow the same directions
as above but align the hairline in the
mirror over the center of the compass and
align the notch on top of the mirror with
an object. 


Magnetic
declination:
Plotting
a heading on a map:


Place the compass
on the map with the edge of the compass
along the desired line of travel. 



Ignore
the needle!
Rotate the compass housing until N on the
dial points North on the map. Check that
the compass housing red/black north/south
lines are parallel with the maps
meridians. 


Calibrating
the altimeter:
Contour
line:


