Re: distance from Easter Island to Chile

[Thorsten Jolitz <tjolitz@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Barry Margolin <barmar@alum.mit.edu>
>> Date: Sun, 20 Apr 2014 03:01:36 -0400
>> 
>> In article <mailman.19905.1397975330.10748.help-gnu-emacs@gnu.org>,
>>  Eli Zaretskii <eliz@gnu.org> wrote:
>> 
>> > This is inaccurate (Earth is not a sphere).
>> 
>> How accurate does your input have to be for that to be a significant? 
>> I.e. if you're calculating the distance between two cities, and each 
>> city is 5 miles wide, the distance is +/- 10 miles depending on where in 
>> the two cities you decide to get the coordinates from. So if the error 
>> in the formula is 2 miles, it's less than the inaccuracy in the input, 
>> so the formula should be good enough.
>
> No one said that these calculations are only for distances between
> large cities.
>
> Anyway, the error induced by assuming spherical Earth can be up to 1%,
> which is not insignificant when the distances are on the order of
> magnitude of many hundreds of kilometers (3757 km and 4301 km values
> were cited by the OP).

I think one of the two French guys who had the task to establish a
world-wide accepted meter unit as 

,-------------------------------------------------------------------------
| 1/10,000,000 part of the quarter of a meridian, measurement (1795) by   
| Delambre and Mechain (http://en.wikipedia.org/wiki/History_of_the_metre)
`-------------------------------------------------------------------------

figured this out the hard way and became a depressed alcoholic because
of an unexplainable 300m 'measurement-error' in his triangulations.

-- 
cheers,
Thorsten