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    Re: Lat/Lon by "Noon Sun" & The Noon Fix PROVE IT
    From: George Huxtable
    Date: 2009 Apr 25, 23:37 +0100

    With Dave Walden's kind help, here are 20 sets of simulated data from
    "around noon", adapted for Jim Wilson's special method of analysis, though
    anyone else is welcome to have a go. The aim is to deduce the position,
    which I have not (yet) disclosed, that on 21 Dec 2008, at 12.40 GMT, is
    somewhere between 55º 30'N and 56º 30'N in latitude, and between 9º W and
    11ºW in longitude. The Sun dec. has been taken as -23.442º and the equation
    of time 1min 44 sec (the Sun transiting at Greenwich that much before noon
    GMT). The vessel has a Northerly component of speed of 10 knots +/- 1 knot
    variation (rms), but you are not asked to deduce that. You can presume that
    all necessary corrections have been made to the sextant observations,
    without additional error.
    
    Each set  comprises 13 altitude observations. The first 5 were taken at
    times 1 minute apart from 12:10 to 12:14, then a gap, then a set of 3, 5
    minutes apart, from 12:35 to 12:45. Then a variable gap again, waiting for
    falling altitudes to start to match the values that were seen on rising.
    From time T (which time is given in a column to the right) to time T+4,
    there are 5 more altitudes given, at 1 minute intervals.
    
    In a previous posting I had said that time T would be the the first moment
    that the altitude, observed at whole-minute intervals, fell below its
    previous value at 12:14. In fact, it's turned out that instead, the
    comparison was made with the altitude (which isn't printed) at 12:15, rather
    than at 12:14. I doubt if this will upset Jim's analysis, but if it does, or
    if he needs any other change in the simulation of data, perhaps he will say.
    
    Each data set has, in the rightmost column, an identifier code attached to
    relate each test set with its solution.
    
    Sorry for the delay.
    
    George.
    
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
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    File: 108048.noon3d.doc
    File: 108048.noon3d.rtf
       
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