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    Re: Advancing LOPs for precision fixes
    From: Peter Hakel
    Date: 2010 Feb 18, 11:04 -0800
    Yes, I implemented the method in this spreadsheet:

    http://www.navigation-spreadsheets.com/lops.html#many_body_fix

    I am now glad ;-) that I am not the only one who found this section of the N.A. not so clearly written.  It indeed requires a little bit of detective work from the reader.  It does not explicitly state that this method employs the dead-reckoning formulae from the preceding subsection.  Fortunately the associated example is worked out in detail and its description refers to a common time for the fix and the individual times for the sights.


    Peter Hakel



    From: Gary LaPook <glapook@pacbell.net>
    To: NavList@fer3.com
    Sent: Thu, February 18, 2010 2:41:00 AM
    Subject: [NavList] Re: Advancing LOPs for precision fixes

    Have you tried using the method in the N.A. to which you refer? I may be missing something but I don't see anywhere in the given formulas where you input course and speed which would be necessary if the method was allowing for advancing the LOPs to a common time.

    gl


    P H wrote:
    > As John Karl writes in his book:
    > "The Nautical Almanac gives an iterative procedure for calculating a fix from several intercepts and azimuths determined from their St. Hilaire sight reductions."
    >
    > I would add that this procedure does take the vessel motion (assumed to be constant during the round of observations) into account.  I am confident that I am simply restating a fact that is well-known among NavList members.  Also, I think it is not unreasonable to assume that the content of the Nautical Almanac reflects common (standard, recommended, accepted, etc.) practice.
    >
    >
    > Peter Hakel


       
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