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    Re: Poor St. Hilaire
    From: Gary LaPook
    Date: 2007 Oct 29, 01:19 -0700

    Gary LaPook writes:
    I learned something new in this discussion.  I had never heard that the
    Sumner method had evolved into using just one point and an azimuth to
    plot the "tangent" method. It may have been easier computationally after
    azimuth tables were available but I think that plotting two points on a
    chart and connecting them with a straight line is easier and less prone
    to error and inaccuracy than plotting an azimuth. This is especially
    true since you can choose the latitudes that are lines already printed
    on the chart with tick marks showing the longitudes. By the time you
    walk a parallel rule across the chart from a rose you are bound to lose
    some accuracy. This is also a problem with the St. Hilaire method so the
    original Sumner "chord" method would appear to allow the most accurate
    plotting of the LOP and a calculator today makes fast work of the
    frankreed{at}HistoricalAtlas.net wrote:
    >Gary, you wrote:
    >"Today, with programmable calculators, it is trivial to go back to
    >Sumner's method and plot the LOP after determining two points using
    >the "time sight" computation."
    >Right. And one advantage of the Sumner approach compared to the St. Hilaire
    >intercept approach is that you can use any old graph paper, including graph
    >paper drawn up on the spot. With a Sumner line, it doesn't matter if you
    >have the correct local scale for minutes of longitude. Sumner himself erred
    >by suggesting that his lines should be drawn on a Mercator projection, and I
    >suspect it slowed the adoption of the method.
    > -FER
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