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
    or...
       
    Reply
    Re: Meridional Distances
    From: Chuck Taylor
    Date: 2002 Sep 17, 19:32 -0700

    Peter,
    
    In an earlier response I mentioned an error in the formula for Meridional
    Parts as given in Bowditch 1995.  I am happy to report that it (a missing
    exponent) has been corrected in the online version at
    http://164.214.12.145/pubs/, and presumably in later printings.
    
    At 10:09 AM 9/18/2002 +1000,  Peter wrote:
    
    >My new (again, new to me) formula for rhumb line goes
    >
    >Arctan course = DLON/DMP
    >
    >Distance = DMD/cosCourse
    >
    >where:
    >DLON means the difference in longitude expressed in minutes of arc
    >DMP means the difference in Meridional Parts
    >DMD means the difference in Meridional Distances
    
    The standard formulas for Mercator Sailing, using your notation, are
    
    Course = arctan( DLON/DMP )
    
    Distance = DLAT / cos( Course)
    
    where DLAT means the difference in latitude in minutes of arc.
    
    These formulas are given in paragraph 2417 of Bowditch 1995 and paragraph
    1007 of Bowditch 1981 Volume 2.
    
    >there is a separate, rather more complicated, formula for when the
    >course lies close to east or west.
    
    The use of a separate formula for when the course lies close to east or
    west is characteristic of Mid-Latitude Sailing.  Like Michael Wescott, I
    suspect that what you are looking at is some sort of hybrid method.  Would
    you mind giving us a reference that describes the method?  I have never
    heard of a table of Meridional Distances, only Meridional Parts.
    
    Chuck Taylor
    Everett, WA, USA
    
    C
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    Posting 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