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: How good is St. Hilaire?
    From: Peter Hakel
    Date: 2010 Feb 27, 10:39 -0800
    Not so long ago I did similar tests of this iterative procedure with input data for only two bodies and assuming a stationary vessel.  First, it was nice to see that the results agreed with the two direct two-body fix methods that I use.  Now in this case we have two equally good geometric solutions.  Therefore, I also tried all kinds of initial DR positions and the method always converged to one of them.  Depending on where you place your DR, the algorithm will march toward one or the other LOP intersection.  I have not studied this further, as it is a rather academic question, but it would be an interesting exercise to rigorously determine the associated "bifurcation" set of locations for this method.  I think I'll keep this problem in reserve in case some eager math student comes to me searching for a project. :-)


    Peter Hakel


    From: George Huxtable <george@hux.me.uk>
    To: NavList@fer3.com
    Sent: Sat, February 27, 2010 5:52:40 AM
    Subject: [NavList] Re: How good is St. Hilaire? was: Advancing LOPs for precision fixes

    [parts deleted by PH]

    Anyway, recently, I tried spooking that algorithm by providing it with an
    initial  DR position, that's the exact antipode of that given as a starting
    DR position in the almanac; that is, E165º, S32º, instead of W15º N32º, with
    everything else unchanged. But it wasn't spooked. It took all of 9
    iterations to work its way around the World from that absurd starting point,
    but ended up once again, back at the same best-position.

    So it seems a robust algorithm.

    George.


       
    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