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: Measuring (and Calculating) Dip
    From: Brad Morris
    Date: 2013 Mar 19, 15:39 -0400


    If it yields the exact same result as (h-h'); where h is height of eye and h' is 1/2 of the peak to trough wave height; then either both are bullshit or neither are bullshit.

    And yield the same result they do. 
    Perhaps you can offer a case where they differ by a "significant" amount.  Significant being left to your perogative. Please don't offer the case where the height of eye is less than 1/2 the wave height, we can see that doesn't work for (h-h') either.  The table stops at zero.


    On Mar 19, 2013 3:27 PM, "Frank Reed" <FrankReed@historicalatlas.com> wrote:

    Brad Morris, you wrote:
    "The wave height correction is by atan((wvht/2)/(3860*sqrt(h))"

    Oh my, oh my... Brad, this equation is bullshit. I should have been more blunt in my previous explanations. I really thought that if I spelled it out to you carefully and slowly, you would see the issues yourself without the need for blunt language. I guess not.

    The correction for wave height is simple: your height of eye should be measured from the tops of the waves as nearly as possible. If you're on a vessel on open water, you can look over the side and see those wave tops. If you're at some protected location, either on shore or in a cove or some other protected waters, you should count your height of eye from your best estimate of the wave tops at the horizon. NO OTHER CALCULATION IS REQUIRED.

    Here we see another problem with mathematics in celestial navigation. Sometimes folks get hooked on the "appearance" of accuracy and mathematical sophistication that comes with a "complicated" equation when the real solution is both "seat of the pants" practical and mathematically elegant.


    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com

    View and reply to this message: http://fer3.com/arc/m2.aspx?i=122961

    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