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Posted by tombh 17 hours ago

Show HN: Algorithmically finding the longest line of sight on Earth(alltheviews.world)
We're Tom and Ryan and we teamed up to build an algorithm with Rust and SIMD to exhaustively search for the longest line of sight on the planet. We can confirm that a previously speculated view between Pik Dankova in Kyrgyzstan and the Hindu Kush in China is indeed the longest, at 530km.

We go into all the details at https://alltheviews.world

And there's an interactive map with over 1 billion longest lines, covering the whole world at https://map.alltheviews.world Just click on any point and it'll load its longest line of sight.

Some of you may remember Tom's post[1] from a few months ago about how to efficiently pack visibility tiles for computing the entire planet. Well now it's done. The compute run itself took 100s of AMD Turin cores, 100s of GBs of RAM, a few TBs of disk and 2 days of constant runtime on multiple machines.

If you are interested in the technical details, Ryan and I have written extensively about the algorithm and pipeline that got us here:

* Tom's blog post: https://tombh.co.uk/longest-line-of-sight

* Ryan's technical breakdown: https://ryan.berge.rs/posts/total-viewshed-algorithm

This was a labor of love and we hope it inspires you both technically and naturally, to get you out seeing some of these vast views for yourselves!

1. https://news.ycombinator.com/item?id=45485227

376 points | 152 commentspage 4
croisillon 11 hours ago|
Related: https://news.ycombinator.com/item?id=34609865
em-bee 15 hours ago||
how close is this to the theoretical maximum?

if we put mt. everest on a sperical cow, i mean on a planet with only ocean, how far could you see there? how far away could a second peak of the same height be, before it gets hidden by the curvature of the planet?

laci37 14 hours ago|
If we have a 9 km mountain on an otherwise spherical planet (r=6371 km), the horizon would be 339 km away. With two mountains having a sightline between eachother the maximum theorethical distance doubles to 678 km.
tombh 14 hours ago||
Exactly.

And it could even be tweaked slightly with some favourable refraction.

stockresearcher 12 hours ago||
Ah, well NASA left some mirrors on the surface of the moon so with some favorable reflection and infinite quality optics, you can theoretically see halfway around the world.
cozzyd 6 hours ago||
I was wondering if this used a Gnomonic projection but the AEQD makes way more sense here (especially if defined in polar coordinates, as I imagine it must be? Then you only need to project the points you actually use?).

Any chance of writing a QGIS plugin with the algorithm?

kawfey 10 hours ago||
The ham radio microwave community thanks you.
12ian34 6 hours ago||
this is very cool, but i want to see photos!
ourmandave 15 hours ago||
Hopefully this won't become a tool for the Flat Earthers. =)
emiliobumachar 15 hours ago||
Might be a tool against them. Note that Mt. Everest isn't on the list. If the Earth was flat, all the tallest peaks would be seeable from one another unless a specific peak taller than one of them was exactly in the way.
tombh 15 hours ago||
We're actually thinking of writing a SIGBOVIK paper where we explore running this whole thing for a Flat Earth!
alansaber 14 hours ago||
This is the geography I was promised in school
IshKebab 13 hours ago||
Can you actually see anything in real life though?
tombh 11 hours ago|
The longest and second longest haven't been photographed yet, but #3 has https://www.guinnessworldrecords.com/world-records/66661-lon...
sandos 14 hours ago||
I mean this is coming to the same result as heywhatsthat, apparently using the same dataset. Sadly it is not really correct, in that I think it blends a lot of things, including TREEs into the height. Its very obvious many places that some height is just not true, unless you account for buildings and treetops.

I believe I _might_ have a 33km view FROM MY ROOF, from 2m above ground I have much less than 1 km.

keepamovin 11 hours ago|
And yet all you have to do is look up to the stars and you can see millions, trillions of kilometeres away. Starlight straight line of sight in so many directions. Almost nothing in the way. Crazy.

This is cool tho. What about to an ocean point from a mountain? Was there anything longer?

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