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: Latitude by Lunar Distance
    From: Lars Bergman
    Date: 2006 Oct 18, 08:59 +0200

    Some comments on George's "adding together 14 numbers, each varying
    randomly in the range between -.05' and +.05' ", in [NavList 1433]. 
    As the variation in each number is due to rounding error, we can assume
    a uniform distribution for each variable. The standard deviation of a
    uniform distribution is the interval length divided by sqrt(12), i.e. in
    this case 0.1'/sqrt(12)=0.03'. Adding 14 such distributions results in a
    nearly normal distribution with standard deviation 0.03'*sqrt(14)=0.1'. 
    In such a normal distribution, the probability of an error in excess of
    0.19' is 6%, and 68% for an error less than 0.1'. This corresponds
    pretty well with George's brute-force simulations, as it should.
    With Frank's assumed distance measurements within 0.1', no timing errors
    and presumably negligible almanac data errors, furthermore assuming a
    "good cut" between the lines; we get a resulting standard deviation of
    say 0.08'. Using a "positional error multiplier" of 60 gives us a "less
    than 6 miles error" with about 80% probability, less than 9 miles with
    95%. So I think Frank's claim is reasonable, given the stated
    Frank could also claim that although there is 20% probability to have an
    error above 6 miles, there is as well a 20% probability that the error
    is less than 1.2 miles!
    59N 18E
    To post to this group, send email to NavList@fer3.com
    To unsubscribe, send email to NavList-unsubscribe@fer3.com

    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