A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
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.
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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