Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    Name or NavList Code:
    Email:
       
    Reply
    Re: Datum for Nautical Almanac
    From: Michael Dorl
    Date: 2004 Oct 29, 10:32 -0500

    In reply to my msg, George Huxtable ; wrote:
    
    >The ellipsoidal shape of the Earth is allowed for already in our charts.
    >Instead of taking the Earth as a sphere, in which case all the lines of
    >latitude would be equally spaced, they are redefined as lines where the
    >direction of gravity makes an equal angle with the Earth's axis. This
    >"fiddle" allows to forget about the Earth's ellipsoidal shape, though it
    >complicates any exact calculation of the distance from A to B on the
    >Earth's surface.
    
    I understand that declination is independent of the reference spheroid
    provided the spin axes agree.
    
    are the following statements concerning the NA true?
    
       Decl and GHA/SHA are with respect to earth's mean equator and equinox.
    
       Diurnal; aberrations effects are not included.
    
       Diurnal parallax effects are included based a spherical earth of (I
    don't know radius).
    
    The suppositions concerning diurnal effects are made since the NA contains
    no corrections based on position;  the NA corrections depend
    only on observed altitude.
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

    Enter the email address associated with your NavList messages. Your NavList code will be emailed to you immediately.
    Email:

    Email Settings

    NavList ID Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site