Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Why it’s impossible to measure England’s coastline

bbc.com

Post reply on HN
Print view View original

31–40 of 42 posts

Re: Why it’s impossible to measure England’s coastline

#31

Post by avazhi »

vidarh wrote: post #25
avazhi wrote: post #13

I guess I could understand why this would be borderline impossible if you did it manually, but surely today with satellite images and computer vision it really shouldn’t be that difficult to agree on a standard unit and then just automate it. Surely just make the scale human at its smallest (meters works and can get converted from there, assuming you have sufficient zoom level data for the coastline) and call it a da…

The article is not about practical measurements at all. Doing it manually has nothing to do with it. It is explicitly about why the measured length depends on the precision you choose to measure with.

The article spends a lot of time acting like this is some intractable problem and that its intractability is the reason there is so much discrepancy between countries and agencies.

Re: Why it’s impossible to measure England’s coastline

#32

Post by metalman »

Bullshit. Tedious, bullshit. The only rational deifinition of a coastline is that it would be a rough average measurement, as nothing else is possible. Very large areas are washed away daily, and in other places the wind and tide deposit a wide variety of material that does in fact become dry land repleet with trees. The daily shift is likely as much as several miles in storm season. My advice is to put your maths, away, and go for a walk, and contemplate that which will not conform to any or in fact ALL compuational power that exists.

Re: Why it’s impossible to measure England’s coastline

#33

Post by rozab »

barnabee wrote: post #27
thebruce87m wrote: post #26

> A new hiking trail will soon allow travellers to walk around England's entire coast This is a strange concept as there are two countries that share a land border so how do they manage the “gaps”?

The Wales Coast Path[0] links up with it, so (aside from the small gap in Cumbria), you can walk all the way round if you start and end at the Scottish border. There’s also the Hadrian’s Wall Path[1] that allows you to link back into a loop new the Scottish border, though it misses out a section of the English coast in the North East. [0] https://en.wikipedia.org/wiki/Wales_Coast_Path [1] https://en.wikipedia.org/wik…

Similar to Hadrian's Wall, there's the Offa's Dyke Path which roughly follows the Welsh border all the way up.

Re: Why it’s impossible to measure England’s coastline

#34

Post by jstanley »

c7b wrote: post #4
jstanley wrote: post #2

I was thinking about this recently, the way to do is to define a radius, and then imagine rolling a circle of that radius around the outside of the coastline (or around the inside! Define that as well) and then take the length of the equivalent track that never leaves contact with the circle. So you get a different length depending on the radius you choose, but at least you get an answer. You could define the radius…

It's in no way a meaningful solution. If you're settling for a resolution, you don't need a ball-rolling analogy. We already know the length of a given coastline at given resolutions (ignoring the constant changing of the coastline itself). What's practically not feasible is getting every country on earth to agree on the right resolutions. And that's for good reasons, because the desired accuracy depends on many fact…

You don't need anyone else to agree on the resolution.

You can just pick one when you are doing some work that requires knowing the length of the coastline.

I wasn't trying to say that we should all agree on a universal definition and use that for everything? That would be insane. I was just providing a way to get a stable answer for the length of the perimeter of a fractal area.

Re: Why it’s impossible to measure England’s coastline

#35

Post by sota_pop »

arjie wrote: post #20
sota_pop wrote: post #12

How on earth can you write an article that practically plagiarizes the title, mention the paradox, and neither mention mandelbrot nor cite the original paper anywhere!? https://www.researchgate.net/profile/Ion-Andronache/post/Wha...

This kind of comment always strikes me as the textual equivalent of the Youtube thumbnail with the big yellow characters and multiple people making an O face and pointing. The article mentions who observed it in history first, Lewis Fry Richardson, and then links to an encyclopedia article about it which describes Mandelbrot. On top of that, Mandelbrot explicitly named his paper that because he is referencing Richard…

That’s fair, the “practically plagiarize” comment was admittedly harsh and quickly written.It’s obviously an allusion to the paper.

Nevertheless, referencing the LFR work and merely including a link where the paper is discussed feels a little like beating around the bush. The primary article doesn’t seem to use the words “self-similar” nor “fractal” - if you’re only interested in LFR work, why reference Mandelbrot at all?

Re: Why it’s impossible to measure England’s coastline

#36

Post by thebruce87m »

owenm wrote: post #28
thebruce87m wrote: post #26

> A new hiking trail will soon allow travellers to walk around England's entire coast This is a strange concept as there are two countries that share a land border so how do they manage the “gaps”?

Three countries - England, Scotland, Wales.

> there are two countries that share a land border [ with England ]

Re: Why it’s impossible to measure England’s coastline

#37

Post by Projectiboga »

deathgripsss wrote: post #29

Side anecdote, as a kid growing up I watched a documentary about the coastline problem on the BBC and I started thinking about the paradox and infinity and it made me incredibly scared and unwell and then threw up. Has anyone else ever experienced this?

I had a nightmare one night after studying Economic Philosophy. The Thesis, Antithesis, Synthesis struck a subconscious fear. My dream was lightning bolts splitting things up.

Re: Why it’s impossible to measure England’s coastline

#38

Post by Projectiboga »

metalman wrote: post #32

Bullshit. Tedious, bullshit. The only rational deifinition of a coastline is that it would be a rough average measurement, as nothing else is possible. Very large areas are washed away daily, and in other places the wind and tide deposit a wide variety of material that does in fact become dry land repleet with trees. The daily shift is likely as much as several miles in storm season. My advice is to put your maths, a…

At which spot in time? High tide, low tide, king tide? The coastline is never even static over a single daylight period.

Re: Why it’s impossible to measure England’s coastline

#39

Post by BobaFloutist »

colechristensen wrote: post #22
linzhangrun wrote: post #19

Earlier quoted context omitted.

[flagged]

The meaning of "coastline" breaks down far before you reach quantum levels. I challenge you to go to the beach and pick a square inch where the "coastline" splits it half and half, this part England, that part the sea.

This is also ignoring the time component, where individual fluctuations in water will change the measurement, tides will as well on a daily and monthly cycle, and as years go by erosion and global climate change will shrink the land and grow the sea.

Re: Why it’s impossible to measure England’s coastline

#40

Post by qingcharles »

bryanrasmussen wrote: post #21
kelnos wrote: post #10

Earlier quoted context omitted.

Assuming they specifically do advertise that you can walk the entire English coast, then it is accurate, as Wales and Scotland are not England.

unless they have edited they do not say Wales and Scotland are England, they complain the trail is not contiguous, which to be fair might also be implied by the fact that Wales and Scotland are not England but I guess I could see a scenario that allowed made the trail contiguous, which would still allow you to walk the English coast, but also of course allow you to walk some other parts that are not on the coast.

I would assume now that they have added the Welsh path to this one that it is now "technically" contiguous, though not yet circular around the whole British mainland until someone does something about Scotland.
Post reply on HN