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    Re: Problems with AstronavPC
    From: Paul Hirose
    Date: 2004 Feb 15, 23:10 -0800

    George Huxtable wrote:
    >
    > [Using the newly updated values for B(F) and L(F) as Lat and Long, rework
    > the calculated altitudes and azimuths, in 7.2.2, 7.2.3, and 7.2.4, and
    > obtain a new intercept p from (observed alt. - calculated alt.). For this
    > to be possible, the original values for dec., GHA, and observed altitude of
    > the body must have been retained.]
    
    George, that algorithm sounds identical to the direct computation
    method in my 1998 Nautical Almanac (the newest one I have). The
    paragraph that begins "If d exceeds about 20 nautical miles..." is
    reproduced verbatim in the Almanac.
    
    It includes a fully worked reduction, which makes clear that some
    values are retained: "The table shows the intermediate values of the
    calculation for the second iteration. In each iteration the quantities
    Ho, GHA, Dec and t do not change."
    
    Computation of standard deviations and error ellipses are not
    mentioned in the Almanac.
    
    
    

       
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