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    Fw: Advancing COPs Revisited
    From: George Huxtable
    Date: 2010 May 4, 00:16 +0100

    In his attached document advancing-cops-revisited (which I attach once 
    again in case anyone wishes to consult it) Herman Zevering questions 
    whether his proposed (and erroneous) procedure for transferring positions 
    has been challenged. It has. In an piece in the Forum section of the 
    Journal of Navigation, 2006, and again, in the same terms, in a posting on 
    this list on 26 Feb 2010, as follows-
    
    =================================
    
    My piece in the Forum section of The Journal of Navigation, vol 59 no 3,
    September 2006, "An erroneous proposal to allow for travel of an observer
    between two celestial altitude observations", pointed to errors in a
    contribution from Zevering, in vol 59/1, "Dependability of position
    solutions in celestial sight-run-sight cases, Part 1. (Part 2 never
    appeared).
    
    To test his procedure, I proposed a simple example, as follows, which
    presumed a spherical Earth-
    
    1. An observer, at position P1, measures the altitude of a star S1, at 
    (Dec1
    = 0º, GHA1 = 0º), to be 30º.
    2. Then he travels due North by 60 nautical miles,  ( = 1º ) to P2.
    3. From there, he observes another star S2 (then at Dec2 = N 1º, GHA2 = W
    45º) to be at an altitude of 45º.  Where on Earth is he then?
    
    I showed that there were two solutions for P2.
    One was in the Northern hemisphere, at Lat N 46º, Long W 45º, in which case
    P1 was 1º further South, at Lat N 45º, Long W 45º.
    The other was in the Southern hemisphere, at Lat S 44º, Long W 45º, with P1
    situated 1º further South, at Lat S 45º, Long W 45º.
    
    Navlist members can check that those solutions meet conditions 1, 2, and 3
    of the example precisely, by computed altitude tables or by spherical
    geometry, as they prefer.
    
    I then challenged Zevering to apply his proposed procedure to that problem,
    and provide us with initial and final positions for the observer, the
    initial altitude of star S1, and the final altitude of star S2. My own
    estimate was that his final position would be 17' in error, in longitude,
    after a travel of only 60 miles
    
    Zevering's response was printed in that same issue. It was in the same
    rambling style that readers will recognise from yesterday's posting. But
    there was no numerical response to that challenge.
    
    So I say this to Herman Zevering- Provide us with your answers to that
    problem: then, and only then, will I take any of your writings seriously.
    
    ==============================
    
    I have looked through Herman Zevering's long attachment of today, to see if 
    I could discover any response to my challenge, but in all its obfuscations, 
    I have failed to do so.
    
    Just two positions, initial and final, are called for. There the matter 
    rests. I doubt if I will ever get a straight answer, but expect that stream 
    of Zevering documents to continue for ever.
    
    George.
    
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
    

    File: 112948.advancing-cops-revisited-.doc
       
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