Top
Best
New

Posted by tombh 19 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

381 points | 155 commentspage 5
keepamovin 13 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?

lutusp 13 hours ago||
On this general topic, guess how distant the horizon (the "vanishing point") is, across open water, assuming clear weather and a six-foot-tall observer standing on a beach? The answer is a mere six miles.

Next curious fact -- the two towers of the Golden Gate Bridge are perfectly vertical, but the top of one tower is 4.6 cm (1.8 inches) farther away from the other, compared to the bottom of the towers -- because there is a small angular tilt between the towers. Guess why ...

Okay, it's because the towers are independently vertical with respect the center of the earth, are horizontally separated by 4,200 feet, and each tower is 746 feet tall. These dimensions assure that the towers have a distinct angle with respect to each other. It's a small difference, but it's not zero.

I thought about these things (and many others) during my four-year solo around-the-world sail (https://arachnoid.com/sailbook/).

colechristensen 16 hours ago||
It's wild in the upper midwest you can SEE the glacial effects on the terrain better than any topo map I've seen before.
tombh 16 hours ago|
I was wondering that too, that this might be a better visualisation of certain geological features. But I don't have much experience, so can't say for sure.
colechristensen 16 hours ago||
It's a sort of high-pass filter I guess? Using the curvature of the earth to highlight local changes in elevation.
tombh 13 hours ago||
I'm not that familiar with high-pass filters. But yes it's the way it exposes local changes in elevation that is unique. Indeed the heatmap is generated dynamically for every change to the zoom and viewport.
drcongo 17 hours ago||
This is my favourite kind of HN post, and I absolutely love this one. Would love to see photos from each of these views.
tombh 16 hours ago||
Thank you <3

Well there is a photo near our #3 longest line of sight https://www.guinnessworldrecords.com/world-records/66661-lon...

venusenvy47 16 hours ago||
I was looking for those on the website. Maybe we could find some photos on Google Maps that already exist from these locations.
pestatije 17 hours ago||
It be nice to get the 3 or 5 longest distances from a specific point, not just the longestest
umpriel 19 hours ago||
Claps!
ryanbberger 13 hours ago|
Thanks umpriel for the PR, hope you're well!
OhNoNotAgain_99 14 hours ago|
[dead]