Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Tuesday, August 23, 2016

Finding Direction Without a Compass

Preparation and carrying the ten essentials is vital to any outdoor trip.  Map, compass and GPS make up my navigation kit.  Still, the unplanned happens and the magnetic compass may be broken or left at home.  Knowing a few common practices can make a difference.
How can you determine direction without a compass or when the compass is broken?

There are a few viable techniques that can be used to determine direction.  But first, let’s eliminate two methods that are not practical.

Let’s eliminate the old axiom of moss growing on the north side of a tree.  It is just not reliable.

Secondly, dismiss the concept that deciduous trees (e.g., oaks, maples) develop significantly more vegetative structure on a southern exposure.  Generally, one would expect more branch development and canopy on the southern side because of the amount of sunlight received.  This is getting a lot of attention on the internet.  In the Pacific Northwest the Forestry professors that I have discussed this with tell me not to depend on such an observation.

The following are a few methods that are worth remembering.

Perhaps the most accurate method to determine direction is to use the North Star (Polaris). For the backcountry hiker consider that Polaris is fixed in position over the northern pole.  Unique from other celestial stars and planets, Polaris is very closely aligned to the earth’s axis.  Stars and planets rotate around Polaris.  And like the sun, rotation is from east to west through the sky.  Polaris will be found approximately half way between the northern horizon and straight overhead.  In the northern hemisphere, Polaris can found in our northern sky and is never more 1° from true north – the North Pole.  A clear sky without a lot background glow from the light from a city is essential.  Polaris is not the brightest star in the sky. Using the North Star when it is high above the horizon is a challenge.  

Most of our compass navigation deals with sighting objects fairly close to the horizon.  For example, when orienting the topo map to true north, the map is held between waist and chest high and then observing what lies before us.  In such a situation we scan in front and compare visible terrain features to the map.  Most of the time, the hiker is looking straight out not 45° above the horizon.  When pulling the true north bearing (from Polaris) “down from high in the sky” it takes a bit of practice and patience to align the bearing to the horizon where it can be useful.

I recommend taking your compass with you on a clear night and attempt to find Polaris. 
For more information about Polaris read my post

The Sun provides an excellent means of direction finding too.  The ideal situation is one where the sky is bright and relatively free of clouds. 

The first method is called a “shadow stick compass.” In an open area, clear away forest debris and duff.  Place a stick or trekking pole (extended about three feet – longer is better than shorter) into the ground as deep as possible (see image below.)

Notice the shadow moving out from the trekking pole.  At the furthest point of the shadow, place a marker such as a rock, stick or tent peg in the ground.

Twenty or thirty minutes later, place another marker at the end of the moving shadow. 

The markers shown above were placed over a period of one hour, each thirty minutes apart.  A piece of baling twine (yellow) was laid adjacent to the markers to provide reference.  The line of markers runs east west.

To find north, I simply put the toes of my boots next to the markers with my body perpendicular to the yellow line made by the twine.  Facing away from the trekking pole, north is straight in front of me. 

A traditional analog watch (one with an hour and minute hands) can be used to locate north.  Again, a bright sunny day is ideal.

The following is quoted from the US Army field manual FM 21-76 (page 20.)

“An ordinary watch can be used to determine the approximate true north.  In the North Temperate Zone only, the hour hand is pointed toward the sun.  A north-south line can be found midway between the hour and 12 o’clock.  (See image below.)  This applies to standard time; on daylight saving time, the north-south line is found midway between the hour hand and 1 o’clock.  If there is any doubt as to which end of the line is north, remember that the sun is in the eastern part of the sky before noon and in the western part in the afternoon. On cloudy days place a stick in the center of the watch and hold it so that the shadow of the stick falls along the hour hand.  One-half of the distance between the shadow and 12 o’clock is north.”

Figure 1:  Image from Army FM 21-76

A topographic map balances the methods discussed above.  Once north is determined (discussed above) orient the map to north and compare terrain features on the map with the actual contours and features on the ground.  Identify topographic handrails such as rivers, trails, and dominant land features (e.g., mountains tops.)  These features will help guide the hiker’s travel during the day.

Such study of a map and its features builds a mental map of the area.  A mental map and terrain association is great step to determine and maintain direction.
Using Polaris and the “stick compass” can, with practice, provide good direction information.  In my opinion, using a watch to determine direction provides a trend of direction at best.  Trend of direction would be where the hiker is heading in a generally northerly direction rather than a specific bearing.
There are a few more techniques available but these three are easily remembered and don’t require more gear.  It is a fine place to start.

For more information consider:

1.    US Army Field Manual – FM 21-76
2.    Staying Found by June Fleming
3.    The Natural Navigator  by Tristan Gooley

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