Navigation Techniques (Long)
Rodger Morris (rodger@FISHNET.NET)
Mon, 7 Aug 1995 08:00:15 GMT
Bert Austin wrote:
>... At the poles, where there is only
>one longitudinal direction, or at extremely high latitudes what methods
>are used to determine a specific direction? Although most of us may
>never have occasion to need this information, it certainly would be
>interesting information to pass along during map, compass and
Currently, there are several methods one may use for determining one's
1) Global Positioning System (accurate to within meters)
2) LORAN C (accuracy varies, may not work at all in some locations;
generally accurate to within a mile)
3) Omega (7 very low frequency transmitters, 1 mile day/2 mile night
accuracy; coverage does not extend to the Antarctic)
4) U.S. Navy Very Low Frequency (VLF) (21 transmitters, scattered around
the world; used as backup by Omega receivers)
5) Grid navigation (used by the U.S. Air Force; requires special
navigation charts and manual resetting of aircraft equipment upon
entering and leaving this mode of navigation)
6) Inertial Navigation System (INS) (accuracy varies; degrades over time;
needs to be updated on long flights)
7) Celestial navigation
8) Deduced reckoning, aka "dead reckoning" (DR), a corruption of "ded
reckoning" (accuracy varies; degrades over time; must be updated)
I was not trained in grid navigation, as this was generally used by the
Strategic Air Command (SAC), and to a lesser extent by the Military
Airlift Command (MAC), of the U.S. Air Force. Had I been assigned to
Fleet Antarctic Support Squadron 6 (VXE-6, "The Puckered Penguins"),
I would have been trained in this technique.
Of these, GPS, Omega, Navy VLF, LORAN C, and INS generally give both a
true heading and true course readout. Grid navigation gives one a grid
heading, which may be converted to a true heading.
Celestial navigation _can_ give one a "line of position" (LOP) or
multiple LOPs, but not a true course or true heading, per se. For the
purposes of ground navigation, one may then determine the number of
degrees to offset in order to find true north or one's desired
direction of travel. In the high latitudes during the day, one may need
to make at least 3 "sun shots" in order to fix one's position.
Celestial navigation was the technique of choice before the advent of
electronically based navigation systems. It was used by Muslims about
700-800 years ago to navigate across the deserts.
I hope that this information is of some interest to people on SCOUTS-L.
As an observation related to this thread, the use of a piece of rope or
string, coupled with a map, can produce a good DR position if one is
hiking along a trail. Before the hike, determine the length of your
Scout pace. For most people, this approximates 5 feet on level ground
and 4 feet going uphill or downhill (about 150cm and 120cm respectively,
for you metric users out there).
Every 1/10 mile, make an overhand knot in the cord you are carrying.
Upon completing every mile, make a double knot. If you have done so,
you can tell how much distance you have covered at any given point or
time in your hike. This was known as "counting the quipu" in U.S. Navy
land survival training.
The English word "mile" derives from the Latin word "milum". A milum
was 1000 paces (pasos), or about 5000 feet. Thus, on level ground, if
one walks 100 paces, one has covered about 1/10 mile over the ground.
Uphill and downhill, 1/10 mile is about 125 paces. If one is hiking on
a trail, the trail serves as an LOP. If you have kept track of how far
you have gone, you can then apply that distance to the map along the
trail LOP to ascertain your DR position.
At that point, you have an orientation point with which to take two or
more compass LOPs from the surrounding terrain and plot them on your
map to arrive at a navigational fix.
Try it out!
Yours in Scouting,
Rodger Morris <firstname.lastname@example.org>
Assistant Scoutmaster, Troop 852, Camarillo, CA
Ventura County Council, Boy Scouts of America
National Woodbadge 416-18, Philmont, 1973
"I used to be a Beaver..."
Terry Howerton Sakima Group, Inc. SCOUTER Magazine Kansas City