# 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: Round-off
From: Lu Abel
Date: 2009 May 17, 17:28 -0700

```In most engineering schools students are taught to carry out
calculations to at least one more digit of accuracy that is desired in
the final answer and only round at the very end.

I also have to wonder about "0.1' of arc and 0.1 deg of azimuth"   0.1
degree of azimuth is exceedingly hard to measure either with a compass
or to plot on a chart, whereas 0.1' of arc is 0.1 nm, easily discernible
on most mid- to large-scale charts or on a plotting sheet used to reduce
two LOPs to a L/Lo of position.

Anabasis wrote:
> I've never heard of rounding to the nearest whole minute during
> reduction.  That doesn't seem too wise to me.  What I was taught from
> all sources is to carry 1 decimal point at all times (0.1' of arc and
> 0.1 deg in azimuth).  This was for all tabular reduction.  When I work
> with formulae, I am carrying 13 places in my calculator and then round
> to the nearest 10th when I am finished.
>
> Using my tools on paper charts/plotting sheets for Celnav, I am
> usually interpolating by eye, divisions less than 1 minute of lat or
> long and within 1 degree of azimuth.  Better precision in the
> reduction process is generally wasted during the plotting process in
> practice.
>
> If you are using computers to plot, its a whole other story in both
> reduction and plotting precision.
>
> Jeremy
> >
>

--~--~---------~--~----~------------~-------~--~----~
To post, email NavList@fer3.com
To unsubscribe, email NavList-unsubscribe@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)