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: Lat/Lon by "Noon Sun" & The Noon Fix PROVE IT
    From: Dave Walden
    Date: 2009 Apr 16, 08:23 -0700

    The .doc file works great. Thanks.
    
    I took George's spreadsheet and automated it with a macro.
    
    First, I used it to generate 1000 sets of 13 observations.  For each set, I 
    let excel fit the parabola, and find the time and altitude of its peak.  I 
    then find the difference between the resulting latitude and longitude thus 
    calculated and the true values.  Thus for each set of 1000, I get a mean and 
    standard deviation of the error.
    
    Using George's convenient "scatter switches", I tried various combinations.  
    He has four switches. In order, the first turns on/off the scatter in ship 
    speed (if one always uses the nominal 10 knots in the calculation), the 
    second changes the equation of time (as I understand it, changing the value 
    to be calculated as opposed to introducing scatter into the result), the 
    third changes the longitude (same comment), the fourth adds scatter to the 
    observed altitude. In the table below, the switches are listed in order, 
    1=on, 0=off.
    
    As can be seen for everything on, the standard deviation of longitude error in 
    nm is 5.68.  It can be seen the ship speed scatter seems to have a slightly 
    greater effect than the altitude reading scatter.
    
    The 1 mile lat and 5 mile long estimates look pretty good to me. YMMV.
    
    
    
    
    1,1,1,1	min lat	min long	nm long
    mean	0.00	0.19	0.11
    stdev	0.40	10.16	5.68
    max	1.29	48.02	26.85
    0 1 1 1			
    mean	0.01	0.19	0.10
    stdev	0.44	6.57	3.67
    max	1.55	22.64	12.66
    0 0 1 1			
    mean	0.00	-1.00	-0.56
    stdev	0.42	6.73	3.77
    max	1.41	20.77	11.61
    0 0 0 1			
    mean	-0.01	-0.38	-0.21
    stdev	0.44	6.72	3.76
    max	1.14	20.50	11.46
    1 1 1 0			
    mean	0.00	-0.22	-0.12
    stdev	0.05	7.48	4.18
    max	0.25	24.18	13.52
    0 1 1 0			
    mean	-0.01	-0.38	-0.21
    stdev	0.00	0.01	0.01
    max	0.00	-0.34	-0.19
    1 0 0 1			
    mean	0.01	0.17	0.09
    stdev	0.42	9.97	5.58
    max	1.33	32.45	18.14
    
    File:
    dwVERSION2.xls
    --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To unsubscribe, email NavList-unsubscribe@fer3.com -~----------~----~----~----~------~----~------~--~---

       
    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