NavList:

Good Start, Brad !

George had already given a most precious indication in NavList [12591] on Mar 29, 13:20, under the following form :

QUOTE

The position given, at the foot of the page, for "Omahareno" harbour,
within Passe Rautoanui at the NW corner of Ulieres (more commonly named
Raiatea), can be compared with modern values from Google Earth.

UNQUOTE

You can also fully confirm George's indications here :

http://cartotecadigital.icc.cat/cdm4/item_viewer.php?CISOROOT=/oceania&CISOPTR=576&CISOBOX=1&REC=1

Now, when you return to Google Earth, you easily recognise the Ohamaneno area and without almost any doubt (George could fully confirm here since he might have the appropriate nautical chart(s) of the area) the Vessel was anchored very close from position S 16°45'36" and E 208°30'20". Given the geography of this site, this position is most probably determined within less than ONE nautical mile error.

They were adequately sheltered there from the trade winds (from the East) and George could confirm or refute this statement.

*******

Now we can start analysing our results :

Certainly their Latitude was excellent since they were at anchor, so within ONE mile at the most.

How did their Longitude determinations perform ?

The average value of their 4 Longitude determinations was 208°37' , only 7' off to the East of their (most probable) actual position, which is truly amazing !!!

If sticking to my earlier favoured Height of Eye of 24 ft, the average value of my 3 Longitude determinations is 208°24' i.e. 6' off to the West of their (most probable) actual position.

The Average Latitude determination (S 16°33') I have performed here is somewhat disappointing since it is off by 12 NM.

I had expected much better from their data. It somewhat confirms that their observed heights were not taken and recorded with the same utmost care as their Limb(s) Distances. As I earlier indicated, it was "in the air" not to bother too much about getting the utmost accuracy on the heights ... too bad. Also, and for lack of more detailed data, in my computations I have assumed that both heights were recorded at the very same time as the Lunar Distance. Given my aim of entirely "reconstructing" their geographical position just from their published data only, this assumption was the most reasonable or, better stated the "least unreasonable" one. Assuming that all measures occurred at the very same time might also bear and account for a heavy part in the overall Latitude (in)accuracy that I am now observing.

Whatever, from ONLY these 3 main published data (1 Lunar Distance + 2 heights) it is possible here to obtain an independently derived full position in Latitude/Longitude within 15 NM of the true position.

My concluding thought is that this is probably the very best we can deduct and derive from such data only.

Best Regards to all

Kermit
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