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    Re: Certaine Errors in Navigation Corrected
    From: George Huxtable
    Date: 2007 Dec 10, 17:25 -0000

    Gary LaPook wrote-
    
    George, your post confused me because I had also checked Wright's
    figures for the Cape Blanco case and came up in agreement with his
    value. I think you may have read his text incorrectly because I read it
    as giving the longitude of Cape Blanco as 331� and all of his longitudes
    are east. This is where he plotted it on his diagram, 331� east which
    is, as you point out, at 29� west of his prime meridian. This gives the
    difference in longitude of 51� and using this value with the latitudes
    of both places of 51� 32' north and using trig I come up with a distance
    of 1864 NM just as you did and it is within 4 NM of Wright's calculation.
    
    
    =============================
    
    Sorry about that. Indeed, I had confused myself, in misreading a 
    poorly-printed "1" as a half!. Gary is quite correct, that all longitudes 
    that we would call Westerly were treated by Wright as Easterly, measured 
    right round the Earth from his reference meridian. With a bit of thought, 
    that should have been quite obvious. Istead, I jumped to confusions.
    
    I presume (though may be wrong) that Wright didn't have the mathematical 
    tools to check his great-circle distance, as we can do so easily now, in 
    calculating cos (distance) from
    
    sin lat sin dec + cos lat cos dec cos (longitude difference)
    
    In which case, it is indeed remarkable that his geometrical constructions 
    gave such close answers.
    
    George.
    
    contact George Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. 
    
    
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