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    Re: ex-meridian sights - further question
    From: Steven Wepster
    Date: 2001 Feb 14, 7:13 AM

       Most interesting. The Ex meridian method stems
       from ancient times before the good Marc. Ste. Hilaire position line method.
       However it appears
       to be time honoured especially with DOT examiners. What has always
       interested me is
       why not simply use a sight taken 10 or so minutes
       before or after noon ( up to 30 or so minutes
       allowed by ex-merid tables) as a simple P/L. It
       can be used with future or past P/L's to give a
       position. Historically the idea of the ex-merid. was
       that commercially it was most important to have
       a noon position so that distance run  and distance
       to go was known and course fuel consumed,
       slip and the rest of it calculated. Commercially of
       course the noon pos. is still important although
       usually worked from GPS. I dont want to knock
       the users of the ex. merid. its just that I have never
       had a use for it.
    Actually the ex-meridian latitude was invented by the Dutch teacher
    Cornelis Douwes in the 1740s, ie before the steam-driven steel
    vessels. The method was considered very useful because those were the
    days before accurate chronometers were available for use at sea, there
    was no notion of an altitude line of position, and Marc St Hilaire
    wasn't even born yet. The ex-meridian method allows the navigator to
    obtain a latitude fix on days when it is quite cloudy and the sun just
    visible for a few seconds close to, but not at, local noon.

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