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    Re: The Maths behind DSD
    From: Greg Rudzinski
    Date: 2017 Oct 8, 18:11 -0700


    Attached is a graph solution for DSD from page 527 of the 1977 edition of volume 1 American Practical Navigator (Bowditch).  The interpolation tables are linear which normally will be good enough.  Pub 229 uses Italic type and an asterisk where the DSD correction exceeds (0.25').  An eye ball interpolation might be more practical rather than fooling around with graphing or double interpolating. 

    Greg Rudzinski 

    From: Eamonn Sparling
    Date: 2017 Oct 8, 16:38 -0700

    I am new to Astro nav and I like to use pub. no. 229. I think I understand how and when to apply double second
    difference, I will probably never need to. My curiosity relates to understanding the concepts supporting DSD
    and what is he relationship between the DSD and the required (extra) increment value of Hc. This is not intuitive to me.
    I would like if the forum could explain this mechanism, or direct me to the maths behind this concept.

    Thank you, E.S. 


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