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    Re: Silicon Sea Leg 88 questions
    From: Renee Mattie
    Date: 2004 Feb 3, 19:51 -0500

    Peter,
    
    Thanks for your further comments on my work.
    I am quite happy to sharpen my teeth on some
    of the points you bring up.  Our differences
    on question 5 is a matter of DEC.
    I got mine online -- my only source for 2002.
    
    You said
    >I've had another look at this Question 5.
    >... Here are my steps for a noon sight:
    ...
    >declination        + 04 44
    
    For part 5 of Leg 88, we are within a 10th of a minute.
    Hs 054d 48.1'
    IC -000d 02.5'
    Dip -000d -3.0'
    Ha  054d 42.6'
    Ac  000d 15.3'
    Ho 054d 57.9'
    
    I also have (for
    Long 153d 54.8' W
    LAT   038d 46.1' N
    2002 Sep 9 22:12:34 UT)
    
    GHA 153d 50.'
    DEC 005d 06.8'
    Hc 055d 20.7'
    Azimuth 179.9d
    From the National Observatory website.
    Which gives me
    Intercept 22.8 nm AWAY
    
    The big difference here is DEC
    I do not have another reference for GHA & DEC
    for 2002, so I put my faith in the national observatory.
    Where did you get your data?  Which do you trust?
    And why?
    
    Regarding 3), you say:
     > > > 3)
    > > >   78.5d, 1652 nmi via the Rhumb Line
    > > >   67d, 1639 nmi via the Great Circle. (67d for first leg.)
    >
    >By comparison, my answer to nearest tenth of degree or nautical mile
    >078.8d for 1652.2nm rhumb line
    >066.6d (initial) for 1634.1nm great circle
    >is slightly different, implying that you used a different method for these
    >calculations?
    >
    I am using the palm application "Navigate" version 1.5, by Rick Chapman of
    JHU/APL  http://fermi.jhuapl.edu/navigate/index.html
    I assumed the difference between your Nav calculator and mine is the
    ellipsoid used. "Navigate" comes with several.  The author says
    "The default ellipsoid is WGS-84" If you want to go into this in greater
    detail, I'll give you all the inputs I used.
    
    You are correct in noting that I used mainly electronic solutions.  As I
    said, I am a beginner.  I have not yet developed all the skills necessary
    in a navigator.  I was quite unhappy with my initial attempt at a DR plot,
    and will require some practice before my paper work is reliable
    to several tenths of a minute.
    
    I've seen several good suggestions in the DIY plotting charts
    thread that sprang up from my questions.  Do you have more?
    
    You said that you wanted to check your results against the "official"
    answers.  As far as I can tell, they have not been published.
    Dan Hogan has stated that he currently has higher priorities.
    
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