Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Re: Meridional Distances
    From: Vic Fraenckel
    Date: 2002 Sep 19, 21:42 -0400

    I disagree with your assertion. The shortest distant on the  surface of the
    earth is the geodesic (what you call a great circle on a spherical earth)
    passing thru the two points. I believe the azimuth calculated on the ellipse
    between the two points is the direction you would sail (neglecting the
    variation etc.) passing from A to B. The methods you describe make an
    attempt to approximate the geodesic but you cannot deny that the earth is an
    ellipsoid. (I guess you can, but it flies in face of the facts). You also
    cannot deny that the great circle route is a fiction and the shortest
    distance between A and B is the elliptical geodesic (by definition the
    shortest distance).
    My comments should not be construed as meaning that great circle or rhumb
    line sailing is not valid. What ever works works, but it is at best an
    Victor Fraenckel - The Windman                 vfraenc1@nycap.rr.com
    KC2GUI                                                      www.windsway.com
          Home of the WindReader Electronic Theodolite
                                   Read the WIND
    "Victory at all costs, victory in spite of all terror, victory however long
    and hard the road may be; for without victory there is no survival."
    - Winston [Leonard Spencer] Churchill (1874 - 1965)
    Dost thou not know, my son, with how little wisdom the world is governed?
    -Count Oxenstierna (ca 1620)
    ----- Original Message -----
    From: "Paul Hirose" 
    Sent: Thursday, September 19, 2002 7:21 PM
    Subject: Re: Meridional Distances
    | Vic Fraenckel wrote:
    | >
    | > My routines give the azimuth (referenced to true north) of the second
    | > from the first point (and the azimuth from the second point to the first
    | > point - NOT recipricals on an ellipse).
    | Yes, that's what I figured you meant. I don't even know what a
    | reciprocal on an ellipse is. My point was that the Mercator methods
    | yield a rhumb line, which is easier to follow. You simply keep a
    | constant heading throughout the voyage. (I'm ignoring variation etc.
    | for simplicity.)
    | On the other hand, computing the azimuth from Point A to Point B
    | yields the initial heading for a great circle course. However, if the
    | vessel stays on that heading it will miss Point B. The miss may be
    | trivial or huge, depending on distance and the lat/lon of the points.
    | The rhumb line and great circle methods both have their place in the
    | navigator's arsenal.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

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

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

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

    Email Settings

    Posting Code:

    Custom Index

    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