Subject: Re: double line bug & nautical miles<br/>
Date: Nov 25, 2001 @ 22:52<br/>
Author: orc@orcoast.com (orc@...)<br/>
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<div id="ygrps-yiv-1612967423">major salutes grantissimo for you have made my points for me & beyond<br/>
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& that is so purrdy in 6 digits of rigorous truth<br/>
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probably the first time any tripoint coords have been made so well <br/>
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& i am glad to see your own recent question also rewarded  <br/>
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& to offer now yet another moderately immoderate wrinkle to it <br/>
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which i had restrained myself from offering until you flipped from 5555 to 5556<br/>
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& that is <br/>
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what if the neatness of the usnm standard transcended even this metric integrity you have found & can now also be discerned to have originated in logarithmic algorithmic integrity as well at 5555point55555etc meters<br/>
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or is that not even a possibility<br/>
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because i love it as a probability<br/>
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even without daring to imagine how it might affect the accuracy questions you raise below<br/>
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<br/>
<br/>
m<br/>
<br/>
<br/>
<br/>
<blockquote><span title="qreply"> --- In BoundaryPoint@y..., &quot;Grant Hutchison&quot; &lt;granthutchison@b...&gt; wrote:<br/>
<br/>
&gt; Just remembered that MathCAD offers 15-digit accuracy in its<br/>
<br/>
&gt; calculations. With that, it seems that the circumference of the GRS80<br/>
<br/>
&gt; ellipsoid at N45d15m is:<br/>
<br/>
&gt; <br/>
<br/>
&gt;      27760926.8278257m<br/>
<br/>
&gt; <br/>
<br/>
&gt; Converting US nautical miles to metres produced a likely answer to my<br/>
<br/>
&gt; question about the five-decimal definition. If one nautical mile is<br/>
<br/>
&gt; 6076.11549ft and one foot is exactly 0.3048m, then one nautical miles<br/>
<br/>
&gt; is 1852.00000m, which can&#39;t really be a coincidence. The definition<br/>
<br/>
&gt; must have travelled through metres at some point. But was the US<br/>
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&gt; nautical mile defined as *exactly* 1852m, with a subsequent conversion<br/>
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&gt; to feet, or was the conversion made first, accurate to five decimals,<br/>
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&gt; and then the nautical mile defined as exactly that number of feet?<br/>
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&gt; This has relevance only in the sixth decimal, but it would be<br/>
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&gt; interesting to know if all those zeros go on for ever.<br/>
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&gt; It also makes a US league *5556m*, not 5555m as my Dent Dictionary<br/>
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&gt; lyingly told me, and so shifts the longitude of Michael&#39;s tripoint a<br/>
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&gt; little.<br/>
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&gt; The upshot is that west-along-the-parallel gives the tripoint at:<br/>
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&gt; <br/>
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&gt;      N46d15m00.000000s W124d09m19.378084s<br/>
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&gt; <br/>
<br/>
&gt; No better accuracy is possible at present because the matter of<br/>
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&gt; whether a US nautical mile was defined as exactly 1852m or exactly<br/>
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&gt; 6076.11549ft cuts in at the seventh decimal place of the seconds of arc.<br/>
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&gt; <br/>
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&gt; Grant </span></blockquote></div>