Subject: Re: double line bug & nautical miles<br/>
Date: Nov 24, 2001 @ 20:20<br/>
Author: Grant Hutchison (&quot;Grant Hutchison&quot; &lt;granthutchison@...&gt;)<br/>
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<div id="ygrps-yiv-1405678029">Michael:<br/>
<blockquote><span title="ireply"> &gt; it is n46d15m precisely to as many digits of zero as you like<br/>
<br/>
 </span></blockquote>Working to the nearest metre (the US nautical league comes out at a<br/>
pleasing 5555m), I make 3nm US to be .0720365 degrees of longitude<br/>
measured along the N46d15m parallel, which puts your tripoint at:<br/>
<br/>
      N46d15m00.00s W124d09m19.33s<br/>
<br/>
A bit of faffing around with spherical trig comes up with a<br/>
reassuringly close value measured along the west-looking great circle:<br/>
<br/>
      N46d14m59.92s W124d09m19.33s<br/>
<br/>
That 0.08s difference to the south means that the westward line of<br/>
sight comes out 2.5m farther to the south at 3nm than the westward<br/>
parallel of latitude. (The tripoint necessarily also shifts<br/>
submillimetrically eastwards, but not something that can be worried<br/>
about with a boat and a GPS.)<br/>
<br/>
Bon voyage!<br/>
<br/>
Grant</div>