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    Re: AN5954 bubble octant by Bausch and Lomb
    From: Alexandre Eremenko
    Date: 2012 May 9, 09:15 -0400

    Still an averager looks to me more natural than a medianiser:
    an averager cannot spoil the sights that are accurate:-)
    The manual does not say this, but the "medianiser" of this sextant
    can be also used in a different way.
    It records all altitudes measured, and represents them
    "graphically", and you can 
    visually select
    one which is not an outlayer.
    Assuming that your shots are equally spaced in time, you
    also find the time. Or just take the average time.
    On Wed, 9 May 2012, Gary LaPook wrote:
    > Well that is the entire point.  Bubble sextants were developed for use in 
    flight and the accelerations in the plane cause large excursions in the 
    instantaneous measured altitudes, it can vary more than a degree! Since these 
    are random variations, taking the average or the median improves the final 
    result. There is a reason that all the octants developed in the 1930s and 
    used by airlines for primary oceanic navigation through the late 1960's and 
    by the U.S. Air Force though the early years of this century all incorporated 
    an averager.
    > gl
    > gl
    > --- On Tue, 5/8/12, Alexandre E Eremenko  wrote:
    > From: Alexandre E Eremenko 
    > Subject: [NavList] Re: AN5954 bubble octant by Bausch and Lomb
    > To: NavList@fer3.com
    > Date: Tuesday, May 8, 2012, 4:52 PM
    > Gary,
    > ...
    > Now let me repeat what I claimed: if you shoot accurately enough so that
    > your altitude changes monotonically, or almost monotonically,
    > taking median is the same as taking the middle observation and rejecting
    > the rest. Then why bother shooting several times?
    > The median is not better than one shot.
    > It only makes sense when your single shot accuracy is bad,
    > worse than the change of the altitude between the shots,
    > as it happens in your first series, which is not monotone.
    > Alex.
    > View and reply to this message: http://fer3.com/arc/m2.aspx?i=119481

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