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I'll defend trying to get accuracies closer than 1 n.m. for one reason
only.If one strives to use all the techniques of observation,correction and
calculation to obtain an accuracy < or = 1 n.m. while at sea on a moving
vessel then the results from a round of sights will most likely be as
accurate as possible under the existing conditions.Remember that the LOP's
obtained during a round of sights indicate where one was not where one is.I
beleive that there are to many uncontrollable conditions especially on a
smaller vessel to hope for greater accuracy even if all the above techniques
are flawless.On a large vessel the sighting platform is more stable than a
small vessel.The accuracy sought would also depend on where one is.Around
landfall or congestion one would be more concerned with accuracy.Outside of
congested areas of shipping or traffic the accuracy is not as important as
in these areas.On larger vessels in the uncongested areas of the oceans one
strives for the most accuracy one can acheive but should feel satisfied if
one comes up < or = 5 n.m.Sea state,atmospheric conditions,ships
heading,pressure to get the results all play a part in the final result.Take
the following example: ships heading 325* psc. ships speed is 25 kt. sea
state heavy  atmospheric conditions are stormy. Time for a round of sights
we''ll say is 6 min. In the 6 min. of time for the sights the vessel has
moved 2.5 nm.The vessels heading didn't remain at 325* but moved at so many
* to either side of it for x amount of time.The horizon can't be accurately
discurned because of the sea state,atmosphere and the observer moving.The
observer may get the body on the true horizon but could be above or below it
also.I think you get my drift.Remember that the sextant and sight reduction
techniques are much older and open to more variables in interputation and
manufactureing than is modern electronic nav. equipment.Even a bad round of
sights is better than no round of sights.At least one will have an idea of
the position held.On modern large vessels traditional nav. techniques are
not the main position finding tools.What we officers will do,sometimes for a
nice chunk of change,is use traditional navigation through a voyage and the
position obtained that is closest to the actual position of the vessel when
the master calls an end to the evolution wins the pot.I beleive it well to
wring as much accuracy from ones equipment as possible,but think it
foolhardy to compair the resulting position obtained with modern electronic
navigation equipment positioning.

   

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