# 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:
Re: Averaging
From: Bill B
Date: 2004 Oct 22, 16:28 -0500

```>> 1. The body is very likely to be changing
>> altitude in a nonlinear fashion.
>
> Just vice versa: very UNLIKELY.
> Namely: ONLY when near the meridian on high altitude.
> In all other cases it is linear for all practical purposes.

I find myself constantly reevaluating my thinking.  For example I was
attempting to apply a ratio of rate of change of Hc to a predetermined error
due to non-linearity.  Bigger the rate of change, bigger the error.  I now
see that concept is flawed.

I am having trouble with the concept that non-linearity increases as the
body approaches the meridian in all cases.

In the case of the being on the equator at an equinox, the rate of change
throughout the day would be an almost uniform 1d per 4 minutes.  Same at LAN
as at sunrise or sunset.  However, the path of the Sun would close to
perfectly linear.  Insignificant error due to non-linearity.

If very near the PN at summer solstice, rate of change of HC would remain
almost constant throughout the day and would be very close to 0. Yet here we
could compute systematic error due to non-linearity.

Perhaps this was made clear in the equations set forth, but the computer I
use most for cel nav, the one between my ears, was not programmed to
visualize the outcome of a string variables.

I did note the formula provided by Alex included declination.

sinA=sinDsinL+cosDcosLcost

Einstein stated, "Everything should be made as simple as possible, but not
simpler."  Perhaps the above formula is as simple as it can be while still
covering all possible combinations, therefor the rules of thumb only operate
within limits, but not in all situations.

Feedback?

Bill

```
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)