Posted by tombh 12 hours ago
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!
But... I want to see a photo! Or at least what it looks like in Google Earth, with a red arrow marking the furthest point.
It feels like the site is setting you up for the big suspense of the longest line of sight... and then it's just a line on a 2D map.
I think it would also really help if the maps themselves were at an angle in 3D with an exaggerated relief, with the line drawn in 3D, so you can get a sense of how it travels between two peaks.
It seems like you've put a ton of effort into this project. I think with just a tiny bit more work on the page, you could really put the "cherry on top".
And with those visualizations, get it picked up by a lot of major news outlets. This is a really fun story, the kind of stuff newspapers and magazines love to run. It's easily understandable, it's a cool new "record", it's a story of someone's perseverance paying off, and then you show a Google Earth image simulating the view as the payoff. (And from slightly above, if necessary, to take account for refraction.)
EDIT: Here, I used Google Earth to show the two points. Unfortunately it's from high above, since otherwise Earth wouldn't show the pin for Pik Dankova, but it at least gives a general idea of the area:
https://imgur.com/hindu-kush-to-pik-dankova-530km-adbVFwb
And here is the Google Earth link for the view, but it doesn't contain the pins:
https://earth.google.com/web/search/41.0181,77.6708/@36.6644...
Note that technically my link is a slightly longer sightline (longer by 7 km).
Also, there is a local sky island completely nontechnical wanna-be 12. Sight lines from up there are huge--except the two times I've been up there I couldn't see anywhere near as far as the supposed sight lines. Roughly 100 miles before all I saw was a haze. (And in a related thread some time ago one of these sight line plotters was getting it seriously wrong. It failed to show areas I knew I could see, it showed areas I knew were blocked by mountains.)
And like I said, the reason I didn't do it here was because it hid the label on the horizon. But here it is:
https://earth.google.com/web/@36.43138439,78.74038717,4785.2...
But without the label you can't really tell what you're looking at. And the big problem is there's no "sideways" zoom like a telescope. Google Earth effectively treats zoom like altitude only.
In my experience while hiking tall things, the Google Earth view is accurate in terms of what you see, if you manage to get the viewpoint next to the ground like this. And you appreciate that the resolution is obviously limited.
That imgur link is great, I totally see what you mean. So surely there is a way to at least automate linking to these views? I don't know about embedding them cos Google will want money. We're very open to suggestions, and PRs of course! https://github.com/AllTheLines/viewview
Long lines of sight are between stuff at high altitudes because at near sea level the horizon becomes a problem after only a few miles/kilometres.
Well the record for the longest photographed line of sight is in the same region as our #3 longest line, at 483km https://www.guinnessworldrecords.com/world-records/66661-lon... So not far off. And I think that even takes advantage of some favourable refraction. So not only might it be possible to see the longest view. But there may even be longer lines if we were to take into account extreme cases of refraction. Which is certainly something we'd love to try.
> He monitored weather conditions closely to find the right window and right location. After a lot of travelling he arrived at Aksu village. The village wasn't accessible by car due to snow and ice so he hiked to the summit. After 10 hours of climbing, he stood on the summit with moonlight providing enough light to set up his equipment. At midnight, he recalls that the temperature was around -12°C with winds around 8 m/s. He remained there all night capturing panoramic photos. Before sunrise, the wind picked up to roughly 20-25 m/s and the battle of capturing his world record image began. He planned to capture the image at sunrise to improve contrast and whilst he is pleased with the final result, he is already making plans for his next record-breaking image.
But still, that kinda confirms my observation about the pesky atmosphere: even with optimal weather conditions, he still needed the sun lighting up the sky behind the mountains just before sunrise, otherwise they would have blended in with the sky at the horizon...
This also applies for much shorter distances: despite what the publicity photos suggest, you can't see the Alps from Munich most of the time (or only as slightly darker shapes on the horizon), although they're "only" ~ 75 km away. You need really good weather to see them clearly...
You won't usually see them from the ground of course but from a couple floors up with a clear line of sight you do see them quite often.
https://de.wikipedia.org/wiki/F%C3%B6hn#Optischer_Vergr%C3%B...
Sure, you can see the mountains only as "slightly darker shapes" as the parent put it but you could identify individual summits I think.
Or is this just an elaborate silhouette?
Is that a difference? I don't know.
But if we instead quibble over the term "photograph," I'd argue that a photograph of a silhouette of a mountain is absolutely a photograph of a mountain. Similarly, I'd argue that X-ray photography is indeed photography.
Lets take it to its farthest extent: can you take a picture of a black hole?
Dedication, mmm, dedication. Dedication, that’s what you need. If you want to be the best, and if you want to beat the rest. Dedication way you need.
Hopefully that means something to Brits of a certain age ;-)
[1] https://uchile.cl/noticias/205455/astrofotografo-logra-nuevo... [2] https://dalekiewidoki.pl/2025/07/world-record-andes.html [3] https://api.flickr.com/photos/robertoantezana/4994301227/
But the longest possible view isn't to the horizon, it is to another point that can see the same spot of horizon on a reciprocal bearing. And ocean has no such points.
One advantage in NZ is that on a nice day you actually have a good chance of seeing it.
Oh ... clicking on Mt Owen doesn't return the favour ... or the other nearest peaks. But Culliford Hill does show a return back to Ruapehu, 355.4 km. Clicking on Tapuae-o-Uenuku also, as expected, gives a line to Ruapehu: 342.3km.
Mt Cook is high, but has too many other high peaks near it.
Mt Taranaki is isolated, but doesn't turn up any very long distances.
I don't expect any other candidates in NZ.
Update: actual and accidental photo of Tapuae-o-Uenuku from Ruapehu (342 km), seven months ago.
https://www.reddit.com/r/newzealand/comments/1m9p0bh/tapuaeo...
And, as pointed out in a comment, also Mount Alarm 2.5 km further.
What is the longest in North America? Or Europe proper -- not Elbrus (which I've not been to but have been close enough to see, from several places e.g. from a house in Lermontov (~94 km only), summit of Beshtau (93 km), Dombai ski field (~63 km), somewhere on A157 (~50km).
So using that, I would say that the longest line of sight in North America is from Mount Rainier, at 390km, looking North West into Canada: https://map.alltheviews.world/longest/-121.76853942871094_46...
That gives a longest in NZ of 365.3 km from Ruapehu, skirting past close by Tapuae-o-Uenuku (in the Inland Kaikoura Range) to a point on the Seaward Kaikoura Range near the peak of Manakau. Clicking on the actual Manakau peak also gives 365.3 km back to Ruapehu.
I can't seem to find a peak to get a reverse path back to Mt Ranier. Everything I try gets stuck in the Olympic Peninsular. (I was there once ... 1998 or so ... a place called Hurricane Ridge IIRC)
So this is the NZ longest line right https://map.alltheviews.world/longest/173.61386108398438_-42...
One thing to note about finding reverse lines, is that they're not truly mathematically identical because the observer always has a height of 1.65m and the destination is always some point at the surface, therefore 0.0m. It doesn't always make a difference, but it sometimes can.
Anyone with expertise want to comment?
Mountains can rise higher near equator because you have the least gravity there. The whole Earth bulges along the equator. But I don't think it's measurable.
So that large lines of sight are near the equator on a north south axis (or symmetrically south north) is crazy because the high rates of curvature in that direction at those latitudes should give the shortest distance to the horizon on earth, making those lines of sight even that much more impressive!
It is not about highest point from centre of Earth. That's is related to equatorial bulge but irrelevant to the discussion.
Edit: to be clear the difference stems from our coordinates. Our starting points are:
41.059167,77.683333 (me)
41.0181,77.6708 (you)
And our end points are:
36.295364,78.755593 (me)
36.314,78.7654 (you)
Also I calculate the distance assuming the Earth is spherical (which gives 538 km) not the standard geodesic (which would give 537 km).
And in the DEM data I measure the distance from the center of a cell to another (not the edge), while measuring from edge to edge may explain a difference of at most 0.1 km as the DEM resolution is 3 arcseconds.
So clearly we disagree on the coordinates of the exact actual sightline as we have a 7 km difference :-)
Edit #2: clearly the error is on your side. I should have checked this first, but the coordinates you give for the "To" point (41.0181,77.6708) land in a valley with the south view completely blocked so it's impossible to view 500+ km south as you claim. Look at where the marker lands on this Google Maps Terrain: https://maps.app.goo.gl/PgBWxi31WZC6vk3V9
There's two forms of interpolation going on here that I'm not sure you or Dr Dueschle are using. We interpolate a "band of sight" of single a degree for our azithmual projection, but uniquely we also rotate the DEM elevations around all the observers rather than the observer around to see all the elevations.
The effects of the first can be lessened by lowering the band of sight such that we only process half a degree at a time so that we make sure we get more coverage further away. We plan on running some more experiments by rotating to cover more points.
The algorithm is already fairly expensive to run against the whole world so we weren't particularly interested in that level of coverage for the full earth.
For total viewshed area, our algorithm comes in at roughly a percent or so difference which was what we used as our benchmark for correctness.
All this to say, no, we don't think you both are wrong, we've been looking at making ours more accurate. At a world scale that's quite computationally expensive, so we didn't use that methodology for our initial launch. We see our results as validation of yours, not as something we've disproved.
Edit: grammar
The error I've experienced hunting bugs tends to be within about .5-2%. That's a vibe, not an empirical "I've calculated the error to be 1.5%". We definitely expect that bound to tighten as we get access to more computational resources.
I do not think this is numerical however. I think it's more directly related to rasterization, interpolation, and not enough angle coverage. We have fairly good numerical and viewshed tests to double check we don't have weirdness going on there.
I'm afraid I don't have a good answer. I'm sure with future runs will get closer to you and udeuschle.de
I thought of you when we saw Colombia appear so high up in the list, I remembered that's something you'd found too.
Why allow the user to select any arbitrary location on a map and give an answer when you know the answer is most likely nonsense? You don't need to compute for 2 days to accomplish that; you could just make it up.
That it's not taking into account human construction or distances of tens of meters?
Presumably you can walk a little bit and climb on someone's roof to see the claimed 24.7 km. Assuming a sufficiently clear atmosphere, and that there isn't a tall office building in the way or something.
There seems to be some missing data here when it comes to the north face of most Himalayan peaks (for example: Annapurna).
I am willing to believe looking south gives you the longer view, but there has to be some points on the north faces that win out for a northern view.
Fun fact, the view north is so far, clear and reliable weather-wise that the CIA partnered with mountaineers to set up equipment to monitor China's progress with nuclear weapons several decades ago.
I wonder how atmospheric refraction is handled in the calculations for the longest line of sight. Since it (a) strongly affects the line of sight, and (b) depends on temperature and weather, how is a static "world record" possible, or even defined? E.g. objects may appear 400m higher in 200km distance under typical conditions.
We actually have a plan to aggregate world runs together, so that one run as low refraction and a short observer, then another run with high refraction and tall observer. Then instead of rendering longest lines of sight as those singl triangles, we could render them as 2 triangles that represents the extremes of expected visibility.
Definitions:
* Hams: Amateur radio operators.
* QSO: conversation or contact between two radio stations.
* QRP: Low power, typically under 5 watts.
https://www.k0nr.com/wordpress/2021/08/using-1-2-ghz-in-the-...
Additionally, the GPS coordinates might need adjustment, as there are several prominent peaks near both Liborina and Pico Cristóbal Colón (the summit of the Sierra Nevada mountains).
[1] https://earth.google.com/web/search/6%2e75514,-75%2e7222/@6....
[2] https://earth.google.com/web/search/10%2e8467,-73%2e7029/@10...
So you're saying a better title for the Colombian line of sight could be "Pico Lagos del Congo to Pico Cristóbal Colón"? We can definitely change that.
Thought I'm not sure what you mean about the coordinates being wrong? Are you saying that you should be able to see further from Pico Lagos del Congo?
500km? Whee...