[HPFGU-OTChatter] Central Scotland

[Shaun Hately]

On 9 Jul 2003 at 0:44, David wrote:

> Apropos of reading Shaun's Astronomy posts, he wrote on the main 
> list:
> 
> "The acknowledged geographical centre of Scotland (to the nearest 
> minute) is 56 49' N 4 11' W - between Blair Atholl and Dalwhinnie."
> 
> The nearest minute is about a mile (a nautical mile, in fact).
> 
> I was wondering, though, how is the geographical centre of a country 
> defined?  Is it a question of cutting out the map, and hanging it by 
> the edge at a few points and finding where plumblines hung from 
> those points cross (centre of gravity)?
> 
> David, who thinks the answer ought to be 'it depends' - the centre 
> for radio transmission is different from the centre for goods 
> distribution.

The geographical centre is the location of balance is achieved if a plane of 
0 width was placed on a point.

It used to be done by creating a large cardboard cut out and balancing it 
on a point - similar to the idea you've given here. Today, it's generally 
done by computer - point locations for the entire border are inputed into a 
computer and then averaged.

The precise location of the geographical centre will depend on the 
resolution for the border locations - if you use border locations 10 
kilometres apart, the central position will be slightly different than if you 
use border locations 1 kilometre apart.

Today, for Scotland, they use a very high resolution for this calculation - I'e 
given the location to the nearest minute, but they have worked it out well 
below the nearest second. Nearest minute is easily good enough for my 
purposes - especially as there is some margin for error.

You are certainly correct that the location needs to be determined 
differently for different purposes - that's why I specifically referred to the 
'geographical centre'.

It's just a point for interest - it used to be done as an exercise to show how 
skilled surveyors were - today, it's just a piece of fun with no real validity, 
and is somewhat arbitrary. But it's good enough as a rough location for 
rough astronomical calculations. If you have to choose a point, may as well 
be near the middle.

I'm now redoing them based on the more likely locations mentioned on the 
main list.

Yours Without Wax, Dreadnought
Shaun Hately |webpage: http://www.alphalink.com.au/~drednort/thelab.html
(ISTJ)       |email: drednort at alphalink.com.au | ICQ: 6898200 
"You know the very powerful and the very stupid have one thing in 
common. They
don't alter their views to fit the facts. They alter the facts to fit
the views. Which can be uncomfortable if you happen to be one of the
facts that need altering." The Doctor - Doctor Who: The Face of Evil
Where am I: Frankston, Victoria, Australia