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Posted by tombh 15 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

363 points | 144 commentspage 3
zoobab 14 hours ago|
Cool places to try wifi long shots.

I did some longshots back in the early days of wifi.

ErroneousBosh 14 hours ago|
You'd need to do a bit of work to adjust the timing, I suspect. At 530km the time delay would be around 1.75ms which would be enough to greatly upset WiFi ;-)

You could probably talk between ends using cheap crappy 446MHz 250mW walkie-talkies though.

galangalalgol 14 hours ago|||
This data base could be used to optimally place meshtastic nodes.
1e1a 13 hours ago|||
You could just send raw 802.11 data frames and then receive them with monitor mode on the other end.
ErroneousBosh 3 hours ago||
If I had just re-read Neal Stephenson's Cryptonomicon recently, which I have, I'd say that I'd set up a link using WEP-encrypted 802.11b and hammer data across it with odd little bits here and there designed to generate maximum spy interest.

But then the actual message would be encoded by very slightly favouring the high or low end of the spread spectrum map as a kind of terribly slow FSK.

observationist 10 hours ago||
I found my big summer hike. It's the farthest point that can be seen from the highest point near where I live. I can make the hike and then get some pictures of that highest point, from the farthest point away it has a line of sight.

Thanks for this tool!

tombh 10 hours ago|
Thank you! This is exactly the kind of thing I was hoping people would use this for.
justjash 11 hours ago||
Pretty interesting. I recently got some cheap Meshtastic devices just to play around with and it looks like the longest line of sight from my house is about 20 miles. Might have to leave one at home and see if I can directly connect to it from the general area it is showing.
tombh 9 hours ago|
Thanks, yes this is actually one of the legitimate usecases we hope for from our algorithm.
werds 10 hours ago||
You can see Scotland from Wales! https://map.alltheviews.world/longest/-3.9754324057705617_53...
tombh 10 hours ago|
Yes! It's the longest line of sight in the UK. I grew up in Wales so it was one of the first I looked for.
1970-01-01 12 hours ago||
There was a post here about 6 years ago for a site that calculated line of site for any two points on a map with both the max line of sight and 2D cross sectional view of the terrain difference between the two points. I haven't been able to find it since 2020, but it was awesome.
tombh 12 hours ago||
Could it be this? https://www.udeuschle.de/panoramas/makepanoramas.htm
1970-01-01 12 hours ago||
No, it used a much heavier JS interface and IIRC it also used Google Earth. That is a nice tool, thanks for sharing it.
1970-01-01 11 hours ago|||
It was https://caltopo.com/

https://www.heywhatsthat.com/ is another bookmark that I had lost to time.

sandos 11 hours ago||
heywhatsthat?
1970-01-01 11 hours ago||
I think that was it, thank you for finding it again!

Actually, I was thinking of https://caltopo.com/map.html but your site led me to it.

noosphr 13 hours ago||
Since you have the data could you show how far you can see in every direction rather than the longest direction?
tombh 13 hours ago||
Yes, but, there's one small problem, storing this extra data for the whole world starts to run into the petabytes!
em-bee 11 hours ago||
what if you put a limit on it? like only a dozen views per point, and only views that are at least 100km. or only do this for peaks or points of interest. or some combination like more views for higher peaks, less for lower ones.
tombh 9 hours ago||
Ohh yes, nice ideas.
em-bee 7 hours ago||
i don't know if that makes sense but it could be interesting to split the views of any point into multiple segments, and then for each segment find the largest distance. next between two of these largest views find the shortest view. if the ends of each view are connected by lines the result would be a zigzag circle around the starting point that gives you a rough idea of the visible area.

most points would be on a slope so they would just have a half circle, only peaks themselves would have an all around view.

bartread 13 hours ago||
This would be incredible - please add this!
croisillon 10 hours ago||
Related: https://news.ycombinator.com/item?id=34609865
alvsilvao 14 hours ago||
This is so interesting. Thanks for sharing. I have been working on a similar project where instead of finding all the sights I have focused on finding all the cycling climbs in the world. I think there is a sense of satisfaction in finding ALL of something.

Cheers

www.climbs.cc

cozzyd 4 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?

12ian34 5 hours ago|
this is very cool, but i want to see photos!
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