Central Scotland

[David]

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.