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: Bowditch
    From: Noel Casey
    Date: 2001 Jan 29, 5:59 AM

    This is a well known limitation of the arctangent(x,y) function as being
    ambiguous  for angles greater than 90 deg.
    The function Arctangent2(x,y) resolves the issue. I don't know if the VAX
    compiler handled that.
    In excel spreadsheet there is the atan and atan2 functions, with the atan2
    function being preferable in all cases.
    
    > -----Original Message-----
    > From- Roger M. Derby [SMTP:derbyrm{at}SEIDATA.COM]
    > Sent: Friday, January 26, 2001 7:45 PM
    > To:   NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    > Subject:      Re: Bowditch [was Re: Hi (WAS: RE: ping)]
    >
    > Just a word of caution that I'm sure is unnecessary.  When I was
    > programming
    > a VAX to do great-circle calculations (path length and departure) using
    > the
    > equations from Bowditch, I got some very strange results.  These turned
    > out
    > to be caused by the machine's math library making different assumptions
    > about quadrant than was used by Bowditch.  I finally made up a table of
    > entries for two points a few nm apart using paths that hit all four
    > quadrents and the four cardinal points and then checking against
    > "reasonable" answers.  Had to add several IF-THENs before Singapore was a
    > long way from the Lizard and in the correct direction.
    >
    > Roger
    >
    
    
    * ** *** ** * ** *** ** * ** *** ** *
    This email and any files transmitted with it are confidential and
    intended solely for the use of the individual or entity to whom they
    are addressed. If you have received this email in error please notify
    the system manager.
    This message has been scanned for viruses.
    
    * ** *** ** * ** *** ** * ** *** ** *
    

       
    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