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
    Curve fitting for noon Sun
    From: Rafael C. Caruso
    Date: 2020 Jan 12, 08:33 -0800

    I am a beginner in the study of celestial navigation, despite being of retirement age, and this is my first NavList posting. My initial celestial navigation project was to try to determine latitude by noon sun, to start with an easy measurement (particularly when carried out from the boardwalk in Belmar, New Jersey, rather than aboard a sailboat). The results were very encouraging, since the measurement error with respect to GPS latitude was only 3.3 minutes of arc, probably a case of beginner's luck.

    I followed the method I read in a couple of textbooks, which recommend taking a series of measurements before and after local apparent noon. What I did not read is which type of curve should be used for fitting these data points. As the data points seemed to describe a parabola (figure NoonSun), I used a polynomial of degree 2, which has the advantage of being easy to deal with (figure NoonSunFit). It also allows a calculation of the time at which the curve reaches its maximum, and of the altitude reached at the maximum.

    My question is: does Sun altitude as a function of time describe a parabola? Or another curve? Or it doesn't matter as long as the fit is acceptable? Many thanks in advance for your input.

    File:


    File:


       
    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