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
    Name or NavList Code:
    Email:
       
    Reply
    Re: Position from altitude and azimuth.
    From: Peter Hakel
    Date: 2020 May 11, 17:21 -0700

    Hello Antoine, quoting from your message:

    ———————
    As an example, with the following numbers rounded to integer values let's us start from :
    - Tony's Position (i.e. from position N60° E030° , Hello Tony ! ) , and :
    - Dave's Height ( 55° i.e. a sub-astral distance D = 2100 NM ),  and :
    - an Azimuth Az = 030°,
    we get a subastral point at N73°17.4' E124°06.6' hence with LHA = 94°06.6'
    ———————

    In the following I consider the GP fixed at this first location that you gave, and look for the position(s) from which this celestial body can be seen at the given altitude (55°) and azimuth (030°). To that end, I modified my “one-body fix” spreadsheet to process both allowed LHA values. I get these two solutions:

    1) 57° 32.1’ N, 38° 13.2’ E
    2) 60° N, 30° E

    They both give the correct azimuth = 30, as well as the correct computed altitude of 55° (i.e., distance of 2100 NM, see attached), so there is no way to choose one solution over the other without additional information. This looks like the ambiguity mentioned in the Wikipedia link provided by Dave Walden, because here the known (azimuth) angle is attached to the longer side of the triangle (ZD=35° > coDec~17°). BTW, as expected, my original spreadsheet gives solution 1); the “Tony” solution 2) comes from the added, larger LHA path.


    Peter Hakel
    https://www.navigation-spreadsheets.com/navigation_triangles.html#sailings

    File:


    File:


       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

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

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

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

    Email Settings

    NavList ID 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