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    Re: Sumner's Line (Navigation question)
    From: Gary LaPook
    Date: 2006 Feb 15, 01:24 -0800

    Capt. Sumner had to work the time sight twice, doing the math two times
    which was difficult in the days before inspection tables and computers.
    
    Marc De St. Hilaire's contribution was his method that allowed you to
    lay down Sumner's LOP while only doing one computation. Most still cling
    to this method today in spite of the development of compact computers.
    This still means you have to determine an AP, plot it on the chart,
    measure the ZN and measure off the intercept.
    A simpler method is to use Sumner's original system but with a computer.
    A long time ago I programed my handheld calculator to compute the
    latitude of a LOP given a longitude or the longitude given a latitude.
    It automatically computed two such points, one east and one west of the
    dead reckoned position (or one north and one south) so all I had to do
    was plot these two points on the chart and draw a straight line between
    them with a straight edge, no measuring azimuth or intercept, an easier
    way to lay down the LOP and less chance for error. People should
    consider using this new (old) method today.
    
    Gary LaPook
    
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