# NavList:

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

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Re: Poor St. Hilaire
From: Gary LaPook
Date: 2007 Oct 29, 12:53 -0700

```I don't know if it takes exactly the same amount of calculation since
I have never worked the cosine-haversine method. But, we do know that
navigators who were using celestial navigation in the good old days
(end of the 19th- beginning of the 20th century) quickly switched to
the "new navigation" St. Hilaire method of computation so THEY
obviously thought that it was an improvement over the Sumner "tangent"
and "chord" methods. Those navigators "voted with their wallets" so
they must have carefully considered what they were doing. In addition,
the St. Hilaire intercept leant itself to the development of short
tables to make the computation easy such as Weems Line of Position
Book, H.O.208, H.O. 211, and then the modern inspection tables, H.O.
214, etc.

My previous post about the 1919 navigation text (I had incorrectly
stated that it was a 1909 text)

"The description of the Sumner method starts on page 186. On page 212
it
discusses "The New Navigation, " invented by Marq St. Hilaire. On page
213 it states " This is but another method of determining a line of
position, or Sumner line, and among intelligent navigators both of the
navy and merchant marine, this method has almost entirely supplanted
the
old time sight for longitude, and the chord and tangent method for
obtaining the sumner lines..."

makes this clear.

gl
On Oct 25, 12:48 pm, John Karl  wrote:
> Gary is right about everything he said - almost.
>
> The Sumner 2-point method and the St. Hilaire method take exactly the
> same amount of calculation, each solving two equations of the same
> complexity.  And Henry agrees.
>
> So all the fuss is about why we use St. Hilaire.  My original point,
> 19 posts ago, was that all the books that I have seen either don't
> explain why we use St. Hilaire, or they explain it incorrectly.
>
> John Karl

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