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George commented about my post about the usefulness of the traditional
noon sight:

"Gary has omitted the most important reason why it was historically so
useful. It didn't call for any knowledge of time."


Well, you do need a calender :-)

gl




George Huxtable wrote:
> Gary wrote-
>
> "There is nothing magic or special about an LOP taken at noon. It is only
> due to its simple computation that made it useful in the past to navigators
> without the necessary math skills to do the trig for a Sumner line of for
> the St. Hilaire method that gave it any usefulness."
>
> Gary has omitted the most important reason why it was historically so
> useful. It didn't call for any knowledge of time.
>
> "Since the normal use of these tables allow you to choose an AP within 30 NM
> of the DR this allows a 4 minute period that you use the tabulated Hc, two
> minutes to the east and two minutes to the west. So certainly using the time
> to one one minute falls into the normal level of accuracy for celnav LOPs."
>
> Gary is referring to the normal use of an observation at LAN for determining
> latitude. There is, indeed, much leeway in timing that observation, just as
> he says.
>
> But Bowditch, rather unexpectedly, read "To calculate latitude AND LONGITUDE
> at LAN, the navigator seldom requires the time of meridian passage to
> accuracies greater than one minute." It's in calculating longitude from
> around local apparent noon that a much better time of the moment of noon
> than to the nearest minute is called for.
>
> George.
>
>
> contact George Huxtable, at  george@hux.me.uk
> or at +44 1865 820222 (from UK, 01865 820222)
> or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
>
>
> >
>
>


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