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    Re: Lewis & Clark
    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.
    
    
    

       
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