Thus far, we’ve discussed the most primitive—but arguably also the most readily useful—application of the sun for navigation, by ready reference to shadows of various objects in the wild, for basic direction finding. When using major terrain features, natural or man-made, as backstops and hand-rails, this is more than adequate, but as we necessarily refine our navigational needs down to more precise destination targets, we likewise need to refine our use of the shadow. As we discussed earlier, the ancient Hellene Pytheas, was able to determine that not only was the world definitively spherical, but that he was progressing further north, along his expedition to Ultima Thule and Hyperborea. Some two centuries after Pytheas, another Greek, this one called Hipparchus, more concretely established the spherical shape of the earth, dividing it into a theoretical 360 degrees. Using the recorded measurements from Pytheas’ journals, he was able to calculate exactly how far north his antecedent had traveled. A few short years later, his contemporary Strabo, a geographer by training, was able to determine that the northernmost recordings of Pytheas, as calculated by Hipparchus were somewhere along the northern coast of that region of what would become France, known as Brittany. Thus was born, at least in the western world, modern navigational theory. As we’ve discussed, Pytheas used a refined, precisely shaped and measured stick called a gnomon, but for less scientific, but still reasonably precise navigation, any stick will suffice. The simplest way for the modern mind to really master the use of random shadows for navigation is to use the shadow stick method to watch the shadows move across the earth’s surface. All that you need to utilize this extraordinarily educational teaching aid is a flat, open piece of ground, no more than a few feet in diameter, that will remain undisturbed for the course of most of a day. Ideally, you will return to this spot frequently during the day, but even if you are only able to check and mark the shadow’s progression a few times during the day, it will work adequately. Conveniently for even the most suburban of students, even a flat spot in your yard will suffice. Equally convenient, while years—even decades—of experience has made this obvious to many self-taught outdoorsmen over the span of human experience, there is nothing that cannot be learned about the sun’s movement across the sky, and it’s application to navigation that cannot be learned by simply paying attention to the shadow stick for most of a single day. On your chosen, clear-sky day, approach your flat, open space as close to sunrise as possible, and drive a stick, anywhere from one to two feet in length, into the ground, standing upright. Look to see where the shadow of the upper end of the stick is cast by the sun. Mark that point. The simplest way to mark it of course, is with a readily identifiable stone, but anything will work, from a spritz of marking spray paint to an old shoe, or even just a piece of wood. While I’ve used a scuffed mark on the ground with the heel of my boot, I don’t recommend that method in most cases. It’s entirely too easy for the wind to blow enough dirt and debris to mask your mark within an hour or two. It also tends to not be precise enough a mark for best results. Wait a little while—a quarter or half hour is adequate, but an hour is not too long either—and check to see where the shadow’s tip has moved. Mark the new location. Continue this for as long—and as frequently—as possible throughout the day, marking each new location throughout. At day’s end, you will have a series of marks remaining. If you’ve been precise in your marking, you’ll soon notice that this line forms a shallow arc around your improvised gnomon. At the middle of the day, of course, the sun was at the highest point in the sky it reached throughout the course of its travel. This moment is the instant when the sun stops “rising” and begins “setting.” While it is not necessarily noon, it is literally “midday” at your location on the Earth. At that moment, it is midday at every point along the meridian—the line of longitude—upon which you stand.1 The line of that meridian runs from the north pole, through your location, across the equator, and then down to the southern pole. How can we tell when this point was during the day? It’s really quite simple: the point during your measurement when the sun cast its shortest shadow was midday. After all, the sun was at its highest point in the sky, right then. Regardless of where you are standing on the planet, the shortest distance between the base of your gnomon and the curve of your arc will provide a perfect north-south axis for your use. How though, do we determine which is which? Which end of your line is south, and which is north? Hopefully, by this point, the answer is self-evident. In the northern hemisphere, the furthest north the sun will ever be directly overhead is the Tropic of Cancer. Thus, if you’re in the northern hemisphere, the southern point of your reference line will always be the base of your gnomon, while the shadow tip arc is the northern end. If you happen to be in the southern hemisphere, the exact opposite is always true. It is only in the tropics—that equatorial region between the Tropics of Cancer and Capricorn—where any thought at all must be utilized to figure north and south, since the sun’s highest point may be north or south of you, depending on the time of year. In that case, it will require some consideration of the approximate date, or at least, the season of the year.2 For anyone who has received almost any survival or fieldcraft training, from Boy Scouts to SERE school, from reading a book or two on the subject, to training with their favorite “bushcraft” guru, it is well understood that you do not need an entire day’s worth of measurements to get a general line of north-south using the shadow tip method. Simple marking the first shadow tip, then waiting a little while—half an hour is usually adequate—before marking the second tip location, will provide a short east-west line that is precise enough to determine the eight cardinal directions, for navigational purposes, with a reasonable degree of accuracy. While that’s obviously not going to provide enough precision to layout azimuths to the nearest degree, it can be—with some practice—adequate to allow you to lay out azimuths to the nearest 45 degrees, or even the nearest 22 ½ degrees with reasonable precision; certainly enough precision to allow you to utilize your topographical map, with a remarkable degree of accuracy. It is also adequate to allow you, as an example, to determine the ideal direction to lay out a shelter or building, to maximize solar exposure for solar gain. In fact, when laying out my solar panel arrays at home, this is precisely the method that I use to mark the back line of the installation, to ensure no magnetic deviation—or mathematical errors on my own part—contribute to interfering with maximum solar gain by my photovoltaic panels. The advantages of knowing PRECISELY where the north-south axis lies are abundant, as we’ll see in future installments of this series, but for general use, the simpler SERE school and Boy Scout Jamboree method will generally suffice. 1Remember this. It will be important later in this discussion of primitive navigation. 2This is an imprecise use of terminology of course, since the tropics do not have “seasons” in the sense that the temperate regions do. While “monsoon” season and “dry” season are spoken of, they tend to not be seasonal in the sense of winter, spring, summer, and fall. Regardless though, the calendar can still be divided by the equinoxes and solstices, providing your seasonal variations that provide guidance on where the sun is in the sky. https://www.patreon.com/posts/primi...paign=postshare_creator&utm_content=join_link Continue reading...
