# NavList:

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

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Response Amplitude Operator
Date: 2013 Mar 10, 16:30 -0700

Hi Frank

You wrote, in regards to dip, the following

You look over the side and see where the waves are peaking relative to your position on deck. Of course, if you're on a small vessel, you have the added complexity of waiting for the vessel itself to be near the tops of the waves if they're large enough.

+++

In my view, the misconception that the vessel you are on will rise and fall to the same amplitude, frequency AND that the frequency of the boat and waves are synchronous is what is holding back our understanding of dip.

While I don't claim to understand the equations, one can see the complex nature of a ships response to waves. Its called the RAO (response amplitude operator). Look at the wiki page for this and you will immediately see my point. While you may sense when your vessel is at the top of its cycle by the acceleration, there is absolutely no guarantee that your vessel is at the "top of the wave". So you are at the high point, is it higher than the apex of the aves or lower.

http://en.m.wikipedia.org/wiki/Response_amplitude_operator

As we have seen, there is clearly a correction for wave height in the calculation of dip, and that it may become significant. This wave height correction will be affected by the up and down response of your vessel to the waves.

It just simply won't be one to one with the waves. Yes, I am aware of all the literature that states "take your sight at the top of the wave". Easier said than done.

Each vessel will have its own RAO, something I alluded to in an earlier response to Greg. This is particularly why a singular dip table, without a wave height correction or vessel RAO correction, seems so unpredictable and wrong.

----------------------------------------------------------------
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
----------------------------------------------------------------

Browse Files

Drop Files

### 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)