NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: AN5954 bubble octant by Bausch and Lomb
From: Alexandre Eremenko
Date: 2012 May 9, 09:15 -0400
From: Alexandre Eremenko
Date: 2012 May 9, 09:15 -0400
Gary, 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. Alex. 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 Eremenkowrote: > > 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. > > > > > : http://fer3.com/arc/m2.aspx?i=119481 > > >