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: Sumner's Line (Navigation question)
    From: Bill B
    Date: 2006 Feb 15, 15:56 -0500

    Henry wrote:
    > It is unnecessary to compute two positions to lay down a line of position
    > by Sumner's method, albeit this is how it was originally discovered and
    > done. The Latitude and Longitude ascertained by a single Time Sight
    > computation, regardless of the Latitude employed, establishes a point on
    > a line of position which is entirely accurate - a line drawn through that
    > position at right angles to the computed azimuth of the body employed is
    > the same LOP as determined by any other method, and just as accurate.
    If I understand, once the longitude is extracted from a given latitude, Hc
    will by default match Ho at that point.  Then the LOP can be drawn at right
    angles to the azimuth from that point?  So all he needed was the current
    azimuth from Hc, latitude, and declination, or George's tangent formula once
    the hour angle was derived?
    It strikes me that in speed reading the online version of Sumner's book, he
    was thinking along those lines when he mused about being able to accurately
    measure an azimuth. I don't know the book well enough to put words in his
    mouth, nor is my history strong enough to know if an azimuth formula(s)
    existed then, but?

    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