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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lewis & Clark
From: Ken Muldrew
Date: 2004 May 26, 11:21 -0600
From: Ken Muldrew
Date: 2004 May 26, 11:21 -0600
On 25 May 2004 at 18:49, Bruce Stark wrote: Re. Lewis & Clark's observations: > It's my view, though, that they weren't entirely sure what they should > have been doing. All too often they would spend a great deal of time > taking observations, then leave out a critical piece of information. > And none of us can argue that the numbers they brought back, or that > have survived, are immaculate. > > Jefferson had wisely advised Lewis not to bother with calculation. > Just take observations and bring the numbers back in understandable > form. Though well intentioned, I think this advice from Jefferson was seriously in error. Had L&C worked their observations, they would have immediately gained an understanding of what information was required. Even if an expert had been assigned to re-work all their observations upon their return, the effort of doing the calculations in the field would still have been worthwhile. I think it would have been the difference between observations that could have been used to construct a map immediately upon their return vs. observations that became mere historical curiosities. In going through the journals of contemporary land navigators in Canada, such as David Thompson and Peter Fidler, one sees the intimate relationship between the courses noted on the journey and the celestial observations. For example, when either of these two explorers worked up a lunar, they first converted all their courses to points of latitude and longitude. Then they take their time sight, usually done just after their lunar, to find the correction to their watch. Using their longitude by account, they then get the almanac values for Greenwich time for the mean time of their lunar observation (interestingly, Fidler always takes 10 observations for a lunar so that he doesn't have to divide in order to get an average, Thompson, either due to his slightly ascetic disposition, or because of his earlier mathematical training, takes only 6 or 7 and does the long division). They use these values to determine the true distance for that particular time (this is the D value that Thompson writes down in his notebook; it is not the cleared distance as assumed by Jeff Gottfred in his Northwest Journal article). They clear the distance (using Witchell's method) and then use the difference between their cleared distance and the true distance to update their longitude by account. The account longitudes are then adjusted for all the courses taken between this lunar and the last, so that the waypoints are closer to the true values (latitudes are updated more frequently with the relative ease of observing the meridian altitude of the sun). With this practice, the explorers have immediate feedback as to the utitity of their observations and whether mistakes have been made. Lewis & Clark didn't have the time to become fully trained in this practice, but their intelligence and initiative were surely up to the task of continuing the learning process during their trek. It should be noted that the Canadian explorers were full-time fur traders; their navigational activities had to be performed so that they didn't interfere with the business of the company--there was no need for a dedicated navigator. Similarly, Lewis & Clark had many other assignments in their mission, but had they been encouraged, they might have been able to work their observations as well (certainly they would have given an enthusiastic attempt). >What the captains needed was written advice on observing, and on > getting numbers read off, recorded, and copied without mistakes. Also > a checklist, so nothing important would be left out. This is reminiscent of Richard Feynman's story about the computing group at Los Alamos. They had an array of people sitting at Marchant calculators with punch cards passing between them, such that different people performed different operations. The programmer would have the cards passed to the different operators in such an order that the desired calculation would be performed. Feynman tells us that he got permission to let the group know what it was they were doing because they were making too many mistakes through carelessness. Once the human computers understood their role in the information processing system, they devised methods for error correction, parallel processing, and other innovations. It was the people who were handling the information who had to come up with these novel techniques, because they had an intimate understanding of the conditions under which they were working. If Lewis & Clark had been forced to work all their observations for, say, the first few hundred miles of their journey, then they would have been ideally suited to produce the type of checklist and notebook that would have made their observations useful, but for a trained astronomer to anticipate the errors that the captains would make on their journey, is unlikely to have succeeded because the atronomer is too far removed from the conditions that L & C would encounter. Ken Muldrew.