NavList:

   

Reply

On 9/11/05 11:54 AM, "Piccer"  wrote:

> I have a Norie's Nautical tables from 1964 which gives a position for
> Trondheim of  63 27 N  09 44 E
> Compare this with what Asbjorn gave us: 63 25,4 N 10 24.7 E
> May-be Asbjorn took his GPS position from a list as did  both Geoffrey Kolbe
> and George Huxtable.
>
> The point I want to make clear is that this mystery about Asbjorn's big
> discrepancy might be explained from a mistake in the starting position.
>
> Thanks George for your warm welcome; I will try to contribute to the
> dicussions whenever possible
>
> Willem Piccer
>
> ----- Original Message -----
> From: "george huxtable" 
> To: 
> Sent: Sunday, September 11, 2005 12:04 AM
> Subject: Re: Beginner
>
>
>> Geoffrey Kolbe wrote-
>>
>>> At 18:13 10/09/2005, Willem Piccer wrote:
>>>
>>>> I was just re-reading the discussion on the problems Asbjorn had and I
>>>> wonder if the whole problem is not caused by the gps position used.
>>>> Especially because he states that the observation height is always less
>>>> than the calculated height.
>>>> I have the feeling that the chart datum chosen plays a role
>>>>
>>>> Willem Piccer
>>>
>>>
>>> The latitude and longitude which Asbjorn's GPS deduces for Trondheim
> (where
>>> Asbjorn says he took the sights) agree with that given in various atlas's
>>> and gazetteers that I have to less than a minute. A glance at the atlas
>>> shows that a position five miles North and East of Trondheim (where
> Asbjorn
>>> would have to be to get an observed altitude 5 minutes less than
>>> calculated) would put him in Trondheims Fjord....!
>>>
>>> Asbjorn would appear to be where he thinks he is.
>>
>> Response from George-
>>
>> Not necessarily so. He would not have to be at the place that Geoffrey has
>> specified, to get an observed altitude 5 minutes less than calculated.
>> Anywhere on a position line passing through that point, and perpendicular
>> to the Sun's azimuth, would fit his observation. So he would not have to
> be
>> in Trondheim's Fjord. Still, it would be useful if Asbjorn would confirm
>> (or not) whether that GPS position corresponds well to his place of
>> observation.
>>
>> There remains something of a mystery about Asbjorn's big discrepancy, in
>> what should be a very accurate observation. Perhaps he will repeat his
>> measurement, next time the Sun shines in Trondheim, and before it gets too
>> low to observe well from his Northerly latitude.
>>
>> And I would like to welcome Willem Piccer's first contribution to this
>> list, from Zeeland, Holland.
>>
>> George.
>>
>>
>> ===============================================================
>> Contact George at george@huxtable.u-net.com ,or by phone +44 1865 820222,
>> or from within UK 01865 820222.
>> Or by post- George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13
>> 5HX, UK.
>>
>
Gentlemen,

Re Mr. Piccer?s 5 min error.  Such an error with a plastic sextant is not
unusual no matter how careful one is. As has been mentioned before,  the
critical areas of a sextant are the pivot of the arm, and the worm screw of
the micrometer.  Granted that plastic injected molding should yield
identical parts, but the assembly is still done by hand.  Any variation in
inserting the pivot, and glueing the holding cap on it could easily
contribute to such an error.  Same goes for the worm screw.  Add in the many
other sources of error that have been discussed earlier, and I am not
surprised at all.

Ken Gebhart

   

Reply