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: Averaging
    From: Fred Hebard
    Date: 2004 Oct 21, 07:13 -0400

    I haven't explored much of this parameter space, so there may be areas
    where I'm dead wrong, but...  as best as I can tell, the only time you
    will see significant (>0.1' of arc) systematic shift will be within 10
    minutes of meridian passage.  That's when you shouldn't average (or
    over long time periods).
    I don't know where these cautions about high altitudes arose.  They
    would be difficult to shoot, just for swinging the arc, let alone the
    distance.  But averaging seems fine, except at meridian passage.
    I know I dodged your question, but tried to answer the intent.
    On Oct 21, 2004, at 1:05 AM, Bill wrote:
    > Thank you Fred,
    > What do you consider to be the upper limit of systematic shift due to
    > averaging that is acceptable, or is that situational?
    > Bill
    >> On Oct 20, 2004, at 7:09 PM, Bill wrote:
    >>> My question, is there a rule of thumb that might indicate when
    >>> averages are
    >>> acceptable and when not.  For example, for error of .4' or less (due
    >>> totally to systematic errors from averaging) difference between
    >>> latitude and
    >>> declination, plus altitude should exceed 60d (or any other number
    >>> that
    >>> the
    >>> gurus decide is reasonable?
    >> Bill,
    >> I'm no guru, let me assure you, but as best as I can tell, as long as
    >> you're 10 minutes away from meridian passage, averages or a straight
    >> line are fine, regardless of declination and latitude.  This is for
    >> short periods, such as 5 minutes.
    >> Fred

    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