Rob Hardy on books


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Navigation without GPS



Rob Hardy






9 October - We did not always have GPS, and we did not always have smartphones, and we did not always know where we were. It still happens that people get lost. At the beginning of The Lost Art of Finding Our Way (Harvard University Press), physicist John Edward Huth tells how there is still danger out there. He once found himself beset in fog, kayaking off Cape Cod. It had happened before, and this time, before setting out, he had noted the waves, wind, and more. He was able to use these clues to get home even in the fog, but two other kayakers were in the same fog and were not so lucky, and he subsequently read about their disappearance in the newspaper. They didn't have his ability to read the signs, and when the fog descended, they probably were completely lost and paddled seawards. His book is dedicated to them, and if Huth has his way, there will be far fewer lost hikers and sailors. There are many primitive and refined methods of land and marine navigation described here. This entertaining book is not just a summary of such techniques, but an appreciation of the pre-smartphone cultures (Arab traders, Vikings, Pacific Islanders, and those scientific types from Europe, too) that used and developed them, and a call for us to lift our eyes from our screens. Huth encourages us to leave "the bubble" of electronic positioning and take a good look around. He has lead courses to train students in primitive navigation and it works. "I have found that students can become adept at reading star patterns, following the arc of the Sun across the sky, and predicting the weather. But to acquire these skills you absolutely must leave the bubble and look at the stars, the clouds, and the Sun."  




What do people do when they are lost? Huth cites a lot of research on the subject, research available because of the many times it happens. Hunters concentrate on tracking prey rather than on getting home, a storm descends and obliterates landmarks, and so on. The problem is not so much being lost and being unable to identify where one is; it is the inability to reorient oneself that is the killer. There is a term for the anxiety for the realization that one is lost: "woods shock," but it can happen to pilots and mariners, too. It can lead to panic and wrongheaded actions; the best advice, if you are literally in the woods and have no way of orientation, is to stay where you are. There is even an International Search and Rescue Incident Database which statistically accounts for the behavior of lost people. Lost people wander out in loopy, ineffective paths that cross back on themselves. If they are observant enough to realize that they are back where they started, panic can increase. Sometimes they use folk advice to rescue themselves, like walking downhill until they find a creek that will lead downstream to civilization; if the stream goes into a swamp, they are worse off. There's a whole list of other ineffective behaviors which lost people perform besides random walks, like following any game trail or track they come across or obsessively attempting to head off in one absolute direction. Some tactics can be effective, like getting to a high point to get an overview of the territory. Huth allows technology to intrude here: a high point is better for cell phone coverage, too. 




Basic land navigation starts with "dead reckoning," which was good enough for Lewis and Clark. If you know exactly where you were to begin with, and you know exactly what course you took and how far you went, you know exactly where you have wound up. The problem is "exactly." (Dead reckoning is used on the sea as well, and works not so well when currents imperceptibly change things.) Huth says you can gain skills in dead reckoning, but that even with a compass an experienced pathfinder can expect a precision within five or ten degrees at best. Estimates of distance covered, based on speed, similarly are subject to distortion due to terrain or fatigue.  




There is a fine chapter on "urban myths" (not entirely a misnomer) about navigation. Everyone knows this one: If you have no compass, you can find direction by consulting moss on a tree, which grows on the north side. "There is a foundation for this concept," says Huth, "but you must be careful." You must be sure you are looking at moss, and not lichen or algae. Not only that, but you have to pick the right trees, and make sure they are not affected by, say, shade from a hillside. Huth will allow that the moss-compass can "provide a crude directional indicator," but only if you know the moss, trees, and local conditions, and if you can average the characteristics of the trees with moss on them. Neophytes are warned not to depend on this guide. Huth goes on to tell how reliable or unreliable the orientation of churches is for finding east, and if you want to go to an unfamiliar city, you can look up the local providers of satellite dishes and then use online calculators to find the direction in which they point. In another chapter, Huth examines the weather folk wisdom in such sayings as, "If dew is on the grass, rain will never come to pass," which he says appears to work. The far more familiar, "Red sky at morning, sailor take warning; red sky at night, sailor's delight," he says is not compelling: "Over the years I have tried to understand this one, and I confess I do not put a lot of faith in it." He tries to explain the possible meteorology behind it, and even mentions the sanction Jesus seemed to give it in Matthew. 




There is of course plenty here about celestial navigation. The description will not be enough for you to grab a sextant, make a sighting, and enter it into tables to get a line of position. Believe me, this is an extraordinarily complicated process, and that it could be done before computers must compel our admiration for the navigators and mathematicians that made it possible. Especially interesting, since we do not here have to consult any of the celestial navigation tables, are corrections navigators have known for centuries they had to make. Light from a star bends as it goes through the atmosphere, for instance, and is especially bent from stars that are close to the horizon; these are just the stars a navigator will be looking for, since the job in sighting with the sextant is to measure the angle between a star and the horizon below it. Horizon effects can be severe enough to cause mirages, and even the best navigator will get inaccurate results if hot air is overlaying a cold ocean; it's the same sort of light-bending that makes phantom puddles appear on a hot distant road. The height of the navigator above the water also has to be taken into consideration. Huth suggests you try this, if you are at a beach and can see the sunset: Lie as close to the water level as you can, watch the Sun go down, and when it just goes over the horizon, stand up. You will be able to see a second sunset, and if you know how tall you are and the times between the first and the second sunset, you can even do a rough calculation of the Earth's circumference. 




Navigators are not restricted to looking at the Sun, Moon, stars, and planets. If you know something about prevailing waves, tides, currents, and winds, you might be able to pick up clues to location; the Pacific Islanders were adept at this sort of wayfinding. If you are stuck at sea and don't know where you are, you might look to the sky to see land-based birds that are fishing but will soon return to land, and they can point the way. Take care not to confuse them with pelagic birds that spend all their time at sea except for nesting. In the old days, when ships and life were slower, a sailor might take a jaunt at sea with no provision for navigation except to ask passing ships about location. Readers of Moby Dick will remember that it was fairly common for ships stop and have a social "gam." Even now, a navigator can get clues from spotting ships in their traffic routes, and Huth explains how even seeing airplanes in the sky can give navigational information. 




Huth's book is sizeable, with good diagrams and maps. He is an inspired teacher, and obviously loves his subject, one that includes cosmology, physics, meteorology, history, legends, and psychology. You may not have a chance of using any of the techniques here. Huth warns, "All of these techniques are matters of habit. Reading about them can be a curiosity, but they need to be practiced." I'm not in mind to practice them, and chances are I am never going to need them, but Huth's guide to guides is fun to read, and is a little monument to human cleverness. 




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