In an emergency or survival scenario knowing a few improvised methods of direction finding can save your life. Pick up nearly any survival manual and you’ll find several methods described to one level of detail or another. One method you’ll find in nearly all of them is the shadow-stick method, which uses the Sun and a stick to determine direction. The concept is rather simple, but there are some things that can get you into trouble that the manuals don’t tell you.
Since the Sun rises in the east and sets in the west, the shadows it casts provide telltale signs of the cardinal directions. To start, find a clear area with full view of the sun and insert a stick of at least 8 inches in length into the dirt. The sun shining onto the stick will leave a shadow on the ground. Use a stone to mark the location of the tip of the shadow (Fig 1, Step 1). This is the western mark. After about 15-30 minutes have passed the sun will have continued to move along its arc westward and your shadow will also have moved eastward. Mark the second position (Fig 1, Step 2). This is your eastern mark. Now draw a line from the first stone to the second and that line will be your east/west line (Fig 1, Step 3). Once the east/west line has been established, knowing north and south are easy. If you think you know which direction home or civilization is, you can use this to plot a bearing to safety. Sounds simple, right? It is but despite what most survival manuals tell you, it’s not always accurate and when it’s wrong, it’s wrong by a lot. Knowing the factors that affect accuracy can save your life and prevent you from walking away from your intended target. When conditions are nearly perfect, you get a terrific result shown below in Fig 2. Unfortunately, conditions are almost never perfect.
Due to Earth’s tilt on its axis, the Sun’s position in our sky varies season to season. In fact the Sun can vary in maximum height by more than 45 degrees from summer to winter. This also means the position on the horizon that the sun rises and sets also varies. Although the Sun rises and sets almost precisely at 90 degrees and 270 degrees respectively on the spring and autumn equinoxes, during the Summer solstice, the sun may rise and set 28 degrees farther north. Of course in winter the Sun will rise 28 degrees south of due east and so forth when it sets. These variations in the Sun rise/set positions wreak havoc on the shadow stick method’s accuracy.
I performed an experiment and created time lapse videos of both the equinox shadow movements and the summer solstice shadow movements. Unusual winter weather prevented me from creating a winter solstice time lapse, but I’ll explain the effects anyway.
In my experiments, buildings and other obstructions preventing a first recording of shadow positions much earlier than 8:30 AM, but all effects would be more pronounced the earlier the readings. Measurements taken at or near the spring and autumn equinoxes produced to the most favorable results. The sun rose due east, traveled very straight and set due west. If you were attempting this method within several weeks of the equinoxes, you’d obtain very accurate east/west readings. Summer produced a much shorter shadows a result of the Sun rising 28 degrees north of east (61 degrees) travelling much higher into the sky and setting well north of west at 298 degrees. This creates a steep parabolic curve. If you were taking readings early in the morning or late in the afternoon, the slope of your line could vary 18 degrees or more, based on when you marked your positions. Winter produces a less severe, but larger parabola, which minimizes the errors seen on summer mornings.
In navigation a compass azimuth error of 1 degree translates into missing your target by 92 feet over a mile travelled. This small error is completely acceptable in most circumstances, but an error of 10 degrees over 5 miles can have you miss by an entire mile. A 20 degree error over 10 miles can put you off course by as much as 3.5 miles. As you can see, the Shadow Stick method if employed without understanding can easily yield unexpected results. As with any survival skill, practicing and validating the effects are important. Remember that just because a guy writes a survival book, doesn’t it’s any good. You must practice and see the effects and compared them to your expectations.
The most important advice I can give is always carry two or more compasses. I have one in my watch and at least two others whenever I venture into the bush. A few Grade-A 20mm survival bubble compasses can be stashed into nearly every pocket or bag, just in case. Although I use these small, accurate, compasses in survival kits, I carry my Silva Ranger or my Tru Nord Backpacker/Survival Compass (Read Review) on most days. I also felt the best way to deal with being in a survival situation is to not get there in the first place. Exercising a little “Lost Prevention” can go a long way.