# NavList:

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

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Re: How to round?
Date: 2019 Jun 12, 15:37 -0400
Tony

It is hard to decide if you are busy hanging noodles or not.  This question begs for a degree (heh) of rational thought.

For CN, as the earth is considered a perfect sphere,  a nautical mile is 1 arc minute  along any great circle.

Your question asks if we should round up or down 1/20 of an arc minute or 1/20 of a nautical mile to 1/10 or to 0/10 of a nautical mile.  1/20 of a nautical mile is 304 feet or ~93 meters.

Therefore, my answer is to round it whichever way makes you happy.  The rounding you are concerned with will not matter for CN, where typical (true) accuracy is on the order of 3 nautical miles.  That's SIXTY times bigger than the rounding value question.

PS.  May I suggest, Tony, that you think about what CN is for, the accuracy you can achieve, and meaningful computation within the context of CN.  To repeat, CN is for crossing oceans.  When you come into sight of land, coastal piloting will resume.  93 meters is insignificant, just as the 3rd decimal digit (0.001° = 3.6 seconds of arc) is insignificant.

On Wed, Jun 12, 2019, 2:04 PM Tony Oz <NoReply_TonyOz@fer3.com> wrote:

Hello!

Consider your further calculations expect a DDD°MM.m' type of input and you have a DDD°MM'03" to proceed.

What do you do, is it DDD°MM.0' or is it DDD°MM.1' ?

In other words, how to round odd multiples of 3 arcseconds?

Regards,

Tony

60°N 30°E

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