Algorithmically Finding the Longest Line of Sight on Earth
39 points by tombh
39 points by tombh
Hello, we're Tom and Ryan, Lobster regulars, that 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 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:
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!
Fantastic venture and poetic that the collaboration started here on lobste.rs. Did you account for the irregular curvature of the earth when calculating view sheds or was that built into the data somehow?
Yeah, it was on Lobsters "What Are You Doing This Week?" thread!
Well scientifically the globe is apparently an oblate spheroid. But we've only assumed it to be a perfect sphere. Considering this is just a first run and that the vast majority of ordinary lines of sight are not of the same order as the longest, we've just assumed that the oblateness is not a significant factor. But we'd love to research the effects more.
Thanks for posting, I was really looking forward to this! I clicked on my (very flat) hometown and it pointed to some distant hills I don't remember ever spotting on the horizon, so next time I'm there I'll have to see if conditions are good enough to see them. :)
Really cool! Love exploring familiar areas through that, looking forward trying this out during a hike one day.
What's also pretty cool is for example checking out line of sight between the Greek island Crete and Gavdos, as a kid we'd travel across the island and were always surprised on the many different points one could still see Gavdos - I guess this would allow you to play that game even further and explore the most furthest away places.
Impressive work and truly wonderful to see the positive impact of lobste.rs on "What Are You Doing This Week" postings. Whilst it's to quite hard understand all of the write-up on a casual afternoon read, it's still great inspiration. Good job both of you on the entire project, including the impressive write-ups and illustrations.
In regards of the longest distance, here is a blog posting that shows an image of how that look like if one tries to take a picture that far (almost invisible).
Do you have an answer on the mirror problem yet?
Aww thanks for the supportive comment. I know that both Ryan and I also enjoy geeky deep dives into niche topics, so it's wonderful to be able to give some of that pleasure back.
So if I zoom in on Gavdos then click on the "In current viewport" line in the Trophy toggle on the right of the map, I get this longest line for the summit of the island https://map.alltheviews.world/longest/24.072783619995192_34.836099668851816
Also I like how the Southern coast of Gavdos seems to be in "shadow", which is really the heatmap saying that it suddenly can't see Crete.
OMG, I remember our comments about the mirrors! Ryan and I have mentioned it couple of times. It has a Travelling Salesman vibes to it. Which actually connects to one of the actual legitimate uses of this whole thing: optimisation telecommunications towers, Wifi mesh networks, etc. So it's certainly on our radar.
Wow, nice! Has anyone ever taken a photo from up there? All I see in your links is maps.
Our #3 longest line has been photographed https://www.guinnessworldrecords.com/world-records/66661-longest-line-of-sight-on-earth
That's especially interesting for ham radio enthusiasts.
That's the third total submission by @tombh, second on the topic with lots of credit to another person collaborating, each with a 4 Months difference. This is generally well accepted within lobste.rs, I personally vouch for that this is certainly welcome and not spam - in contrary, this appears to be a well integrated attempt to participate the community.
Here a lengthy previous conversation on the topic: https://lobste.rs/s/7mx8tx/is_it_appropriate_keep_submitting