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: Dan Allen
    Date: 2002 Sep 17, 16:51 -0700

    On Tuesday, September 17, 2002, at 03:53 PM, Peter Fogg wrote:
    
    > Have recently come across a new (to me) method of calculating rhumb
    > line
    > courses and distances, and also traverse calculations, where the
    > starting position, course and distance are known, and the finishing
    > position needs to be calculated.
    
    The formula is pretty straightforward for this.
    
     From http://williams.best.vwh.net/avform.htm is this:
    
    To find the lat/lon of a point on true course tc, distance d from
    (lat1,lon1) along a rhumbline:
    
       lat = lat1+d*cos(tc)
       dphi = log(tan(lat/2+pi/4)/tan(lat1/2+pi/4))
       IF (abs(lat-lat1) < sqrt(TOL)) {
          q=cos(lat1)
       } ELSE {
          q= (lat-lat1)/dphi
       }
       dlon=-d*sin(tc)/q
       lon=mod(lon1+dlon+pi,2*pi)-pi
    
    (the initial point cannot be a pole!)
    (logs are "natural" logarithms to the base e.)
    (TOL is a small number of order machine precision- say 1e-15.)
    (The tests avoid 0/0 indeterminacies on E-W courses.)
    
    Dan Allen
    
    
    

       
    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