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    Re: Zenith Fixes
    From: Andrés Ruiz
    Date: 2019 Mar 26, 10:02 +0100
    Dave,

    about the subject "Zenith Fixes",
    yes you could call it:
    "fix close enough to the body’s zenith", 
    "fix by sights of stars near its zenith", 
    "Fix by High altitude observations".

    The Fix is obtained in the usual manner.
    Move each observation to a common instant of time. 
    That time for fix is usually the time of the latest sight.
    But with with high speed, it could be better to advance them to a future time.
    It is the same as obtain a fix, and with it calculate your position after some elapsed time steering at COG, SOG
    Of course if the error could be great, (steering , waves, refraction, turbulence in the air, etc) do not advance the fix too much.
    DR/AP/EP serves only as an initial position for the calculation, for nothing more.

    Fix.png

    err = The distance between the assumed position and the improved estimated position in nautical miles
    image.png

    Celestial Fix - n LoPs - by Least squares Sight Reduction algorithm. Paper & Excel

    Andrés Ruiz
    Navigational Algorithms
    http://sites.google.com/site/navigationalalgorithms/

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