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: Which calculator to use for "arctan(tan(269))"?
    From: Robin Stuart
    Date: 2017 Jul 6, 07:28 -0700

    Tony,

            This shouldn’t be too much of a surprise if you inspect spherical triangles that these formulas come from and identify the corresponding sides and vertex angles (see Bowditch 2012, p. 348). By analogy it follows from the earlier discussion that you can get both the great circle distance and course using the calculator’s Pol() function.

    Pol{ [ cos(Lat1) · tan(Lat2) - sin(Lat1) · cos(λ2 -  λ1) ] , [sin(λ2 -  λ1) ] }

    and then

    D = 60 × sin-1( r cos(Lat2) ) and C = θ

    where D is the distance in nautical miles and C is measured eastward from north (again you may have to add 360° to bring it into the correct range).

    The distance will be correct provided the two places are less than 90°apart on the Earth’s surface. If you know the distance is greater than 90° then

    D = 10,800 - 60 × sin-1( r cos(Lat2) )

    Regards,

    Robin Stuart

       
    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