NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

HOME

Re: Waves & Dip
From: Mike Freeman
Date: 2017 Apr 23, 23:48 -0700

Thanks David,

I am just learning celestial but as soon as I read this it confused me. We are all aware waves and swells are never uniform in height but to attempt to consider this factor while working out a sight must be unrealistic. In my considered opinion we must consider the waves & swells are in fact uniform and the view of the horizon is made up only of crests. Therefore we need to take our sight when our yacht is as close to the crest as possible. I understand the horizon we need to use will be parallel to the celestial horizon and a line drawn from crest to crest achieves this. As does a line from trough to trough but the visible horizon is not made up of troughs and our view in a trough is of the face of a wave. A line drawn from half way up a wave to the crests of the waves on the visible horizon is not parallel to the celestial horizon. It is also clear that in unfavourable conditions as with all position fixing we should not be over confident about the accuracy of any fix obtained.

Very happy to have any of the above corrected.

Mike

What is NavList?

NavList is a community devoted to the preservation and practice of celestial navigation and other methods of traditional position-finding. We're a group of navigators, navigation enthusiasts and hobbyists, mathematicians and physicists, and historians interested in all aspects of navigation but primarily those techniques which are non-electronic.

To post a message, if you are already signed up as a NavList member, start a new discussion or reply to any posted message and use your posting code (this is a simple low-security password assigned when you join). You may also join by posting. Your first on-topic messsage automatically makes you a member, and a posting code will be assigned and emailed to you for future posts.

Uniquely, the NavList message boards also permit full interaction entirely by email. You can optionally receive individual posts or daily digests by email, and any member can post messages by email (bypassing the web site) by sending to our posting address which is "NavList@NavList.net". This functionality is similar to a traditional Internet mailing list: post by email, read by email, reply by email. Most members will prefer the web interface here for posting and replying to messages.

NavList is more than an online community... more about that another day.

© Copyright notice: please note that the rights to all messages and posts in this discussion group are held by their respective authors. No messages or text or images extracted from messages may be reproduced without the explicit consent of the message author. Email me, Frank Reed, if you have any questions.

Subject:
Author:
Start date:	(yyyymm dd)
End date:	(yyyymm dd)

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

NavList

What is NavList?

Join / Get NavList ID Code

Retrieve a NavList ID Code

Email Settings

Custom Index

Add Images & Files
Name or NavList Code:	Email:

Name:
	(please, no nicknames or handles)
Email:

NavList ID Code: