1. To find your position using 2 or 3 known points: This is
called triangulation. OK, so you might not know your position exactly,
but you do know enough to
be able to recognize 2 or 3 landmarks. Triangulation allows you to
pinpoint your position.
- Navigation is not about finding yourself after you are lost (although that’s what happens sometimes); navigation is about
keeping track of your position
as you move away from a known point. As you move you have to remain
cognizant of the
terrain you are leaving, of the terrain you are passing, and of the
terrain that is coming up.
Landmarks that are used for triangulation (or for any aspect of
navigation) can be anything
that you recognize as being on the map. Classically these are hill tops,
but you can use the
intersection of two roads, a facility such as a power grid sub-station,
the abrupt edge of a
ridge, the edge of an island, the bend in a trail, anything
that you can recognize as being
on the map and that you can see.
It
is night and you have been wandering in the hills denoted by the big
circle. You are on a
ridge but not sure which one as denoted by the two small circles. You
shoot a bearing to the
highest silhouette to the west, which you correlated to the highest hill
on your map, you get
255°, and draw that line in blue. You see a car’s headlights make a
turn onto Lee Canyon
Rd. You shoot a bearing to the intersection, you get 75°, and you draw
that line in red.
Whoa! 255° and 75° are the same line. They are reciprocal headings,180°
different, however
you are on the highest ground there is between yourself and the
intersection at the highway
and there are no ridges between yourself and the peak to the southwest.
Your position is on
the highest ridge that both lines cross.
The principal of triangulation is to shoot 2 or more points; where those
points intersect is
where you are. In this case the two lines coincided, but a third line
was the ridge you were on.
Thus, you had an intersection after all.
- NOTICE: You did not once need to read a number off the compass.
I
called the bearings out in the above exercise for clarity. Pointing at
each target you turned
the bezel ring until the needle was “boxed”….and on the map
you placed the compass with
the base plate next to the target and rotated the entire compass until
the index lines were
parallel with the grid lines and then drew a pencil line.
2.
- To
find your position using one known point and a linear feature:
In
this example, you could shoot
a bearing to the “get there”
target and start walking overland
but decide that is not your best
option (…and it isn’t!).
You are on a road now and “get
there” appears to be at the end
of a road. You decide to use the
roads.
Your decision is this; set 90° into
your compass, continue walking
up the road you’re on, keep that
“hill” (red dot) in mind and keep
it in view, when you can point
your compass at the “hill” and the
needle is “boxed” you will be on
the road due west of the ”hill”
(green dot), you now set 270°
into your compass, walk about
1.5 km to the road that “get
there” is on (purple dot), then
turn left walk about 250 m and
you’re there.
Thus,
you will use a linear feature (the road you’re on)
and a known point (“the hill”) to find the position on
the road where you want to turn (green dot). NOTE:
Any linear feature will work for this; such as a power
line, wash, ridge, etc. But also the bearing line that
you are traveling on can be used as a “linear feature”.
-
OFFSETTING YOUR BEARING and USING a HANDRAIL:
Let’s
say you have stashed your gear
at the “get here” dot.
If in going from the “green dot” back
to your gear, you were to measure the
bearing and attempt to walk that
bearing directly to the gear, chances
are you will end up walking in circles
looking for your gear.
So, instead you offset your bearing, in
this case purposefully to the right, so
that when you arrive at the linear
feature, the road (purple dot); you
know to turn left, walk 250 m and find
your gear.
This is called ”using a handrail”.
Blindfolded you could find the handrail
and then the gear. Well, I don’t know
about that….but kind of.
-
FINDING YOUR POSITION BY DETERMINING the COMPASS
DIRECTION of the LINEAR FEATURE YOU ARE ON: Use
any feature, gullies, ridges, saddles, roads, especially roads, etc.
1.
You are running down the canyon
from WP 8; you’ve been running and
running and are beginning to wonder
where you’re at.
Standing in the bottom of the canyon
you point your compass down the
drainage/canyon.
Turn the bezel ring of the compass
until the needle is boxed.
-
NOTICE: You do
not need to read a number;
just….
Lay your compass on the map
(forget the needle now) with the
base plate along the blue line of
the canyon bottom and move your
compass around to different
positions until the index lines of the
compass are parallel with the grid
lines of the map AND the base
plate is along the blue line of the
canyon bottom.
