Subject: Re: Fwd: Great circle distances<br/>
Date: Nov 24, 2001 @ 14:43<br/>
Author: Grant Hutchison (&quot;Grant Hutchison&quot; &lt;granthutchison@...&gt;)<br/>
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<div id="ygrps-yiv-123873437">Michael:<br/>
<blockquote><span title="ireply"> &gt; so i have to wonder if you cant simply do this calculation in reverse<br/>
&gt; <br/>
&gt; & if so then voila waorus is fait accompli<br/>
<br/>
 </span></blockquote>Yep, that&#39;s what I was going to do if we were measuring along a great<br/>
circle that started out due west. There&#39;s an approximation in there<br/>
because the great circle is going to slide a tad southwards in the<br/>
3nm, and so ends up over a bit of the earth with a different radius<br/>
from the starting point.<br/>
The maths is easier along the parallel because then all you need to do<br/>
is work out the circumference of that particular parallel in nautical<br/>
miles and do a division. And *that* would be do-able to random<br/>
accuracy within the limits of whatever model of the the ellipsoid you<br/>
cared to use.<br/>
<br/>
Grant</div>