# 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: Azimuth Equation revisited
From: Bill B
Date: 2005 Oct 20, 02:42 -0500

```> Further, while we are on the subject: What exactly is meant by Step 3 on
> pg 279 of the N.A.?  Is it simply that if the value calculated for X is
> greater than 1, then X is assigned the value +1, and hence when A is
> calculated (cos-1 X) it is simply 0 degrees True, and 180 degrees True if
> the value of X is less than -1 (hence = -1)? And what is defensive coding?
> Am I correct to assume simply putting in the If clause in my programming to
> insure that if X>+1, then set it equal to +1 &c.?

You are way above my head with most of your questions.  My question to you
is, "Why make your program, or life, more painful than it has to be?"  It
appears to me that the Almanac creates little nuggets--whatever--to save you
from multiplying the same set of values twice by hand.  Not a  problem with
a programmable calculator.  Use the straightforward formula for Z instead.

Reduce the "if" arguments to:  If sinLHA is positive, then Zn = 360-Z.  If
sinLHA is negative, then Zn=Z.  Why mess with the other stuff?

Hopefully a former discussion on the merits of using tangents or reference
to the archives will resurface.

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)