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This is so clever and interesting. Congratulations!

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...

For a 3D rendering of the longest sightline, see this direct panorama rendering: https://www.udeuschle.de/panoramas/panqueryfull.aspx?mode=ne...

Note that technically my link is a slightly longer sightline (longer by 7 km).

Thanks for the link! It's a very helpful website. It's a pity I can't find any info on the developers for the website.

It even points me to google earth website with the same view: https://earth.google.com/web/@41.059167,77.684167,5853a,0d,3...

Google chrome is probably necessary for openning the site.

Well this is just a personal website, so it is has much (or as little) information as the owner wants to put up. The legal notice page (in German) tells you it's the site of a certain Dr. Ulrich Deuschle: https://www.udeuschle.de/impressum.html

Google Earth shows what it looks like from above. That can be very different from what it looks like from a side view. I've hiked to many spots I saw from above with Google Earth--it can be hard matching up what I see on the ground with what it saw from the sky. It never looks remotely the same.

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.)

Google Earth can produce a side view just fine, it's just not designed for that so it can be tricky to get the position just right with the available controls.

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.

Do you think there's any way to automatically create these Google Earth links for each of the longest lines of sight on maps.alltheviews.world?

There has to be, since it seems to consist of what I assume are fairly straightforward parameters in the URL that encode position and direction.

Looking online, it seems to be:

  https://earth.google.com/web/@<lat>,<lon>,<alt>a,<range>d,<fov>y,<heading>h,<tilt>t,<roll>r

Apparently the tricky part is placing a pin, which belongs to an encoded /data= parameter, and from what I gather nobody's discovered how to set that data.

It seems that it might be possible to dynamically generate a KML file which defines everything (including pins) using markup, but it's not clear if there's a way to pass that or encode it in a single link to Google Earth (as opposed to the user having to manually load it once in Google Earth). Google Maps is basically the same as Google Earth in the web interface, so there might be a way to do these things there.

So it's definitely possible to do something, but figuring out exactly how far you can go might take some experimentation.

That sounds really promising. I've made a Github issue to make sure we follow this up https://github.com/AllTheLines/viewview/issues/61

Thanks!

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

I had a slightly different question (that wasn't googleable), that you may be able to answer with the data you have.... What two points on earth are furthest from each other when taking into account the earth is an ellipsoid? I'm guessing Chimborazo and whatever is diametrically opposed to it, but is there anything else that's close?

There aren't that many antipodes on land. It is mainly South America to Southeast and East Asia. With New Zealand to Spain.

Chimborazo's antipode is Sumatra. That may be the best, unless there is peak in Indonesia that lines up with Andes in Columbia.

Do you mean like if you drew a line from the surface on one side of the planet, through the Earth's core, to the other side of the planet. What is the longest line that could do that?

Yup... Figured it would be interesting if two people stood on opposite sides of the earth and could claim they were as far apart as possible, or if someone visited both "antipoles" and stood at the locations that were furthest apart.

Wooah, both "antipoles", I've never thought of that. What a great idea. In theory yes, we have the data, but I haven't begun to consider the maths to figure that out.

And then you each put a slice of bread on the ground, and have an Earth sandwich.

Also spell out what "line of sight" means in this context.

It means a straight line that you can see to the other end while still being on the ground.

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.

Yes, I worked it out - just a suggestion for making the article better.

Cool project! Unfortunately our planet has this pesky (but very useful!) thing called atmosphere, which makes all these extra-long lines of sight only theoretical, I guess? Ok, the longest line of sight is mostly over the Taklamakan desert, so probably very dry air (which might however have some dust/sand in it), but still?

Thanks!

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.

Wow, that's an impressive amount of dedication, but I guess you need that if you want to set a world record:

> 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...

> 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)

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.

In the northwest of Munich we can see the alps quite often (around 100km from there), and sometimes they appear quite huge. It's due to the Föhn that makes the atmosphere act as a magnifying lens. Interestingly the explanation is not in the English Wikipedia

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.

I think that "magnification effect" is what tombh (one of the authors) means when he mentions "refraction" in his comment above?

Here's the English Wikipedia article (although it doesn't mention the Föhn specifically): https://en.wikipedia.org/wiki/Atmospheric_refraction

Of course, there is another "magnification effect" which photographers like to use: perspective distortion (https://en.wikipedia.org/wiki/Perspective_distortion#Example...). The reason why the mountains seem to be right behind the Frauenkirche in those publicity photos I mentioned (e.g. https://www.technik-testen.net/wp-content/uploads/2023/01/Ad...) might have a little bit to do with the Föhn, but most of it is because the photo is taken from far away and zoomed in.

Putting on my pedantic hat, does this qualify as a picture of the mountains? As in, is there any light hitting the mountains, then hitting the film/sensor?

Or is this just an elaborate silhouette?

Is that a difference? I don't know.

Is a silhouette not a "picture"? Perhaps "picture" isn't the best term to quibble over, since it is quite broad (arguably its primary use is referring to paintings or drawings).

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.

Its a really interesting question.

Lets take it to its farthest extent: can you take a picture of a black hole?

Or how about this: can you take a photograph of a shadow?

> Wow, that's an impressive amount of dedication, but I guess you need that if you want to set a world record

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 ;-)

Roy Castle!

Bingo! Loved that show

funny to know that the record has just been broken, the latest I knew of was by Roberto Antezana, astrophotographer from Universidad de Chile, capturing the Aconcagua (6950m) peak from Cordoba, Argentina, taking advantage of the peak's altitude and the Argentinian pampa (very flat grasslands), and of course, thorough planning + lucky cooperative weather [1] [2]; he was well known before from his long distance photos of the same peak from Valparaiso bay [3], I'm from Valparaiso and the times it was possible to see that peak with the naked eye given some perfect blue sky was truly overwhelming, since then I've been thinking about how to achieve such excursion planning heuristically from topographical data available. Congratulations on your project, I will look more into the technical details but looks amazing, beautiful art and technique!

[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/

Do the two points have to be on land? I would think since you can see the ocean from Aconcagua you'd be able to see all the way to the horizon and that would be the longest sightline

Out of the question. The higher up you are the farther the horizon, I wouldn't be surprised if the longest horizon is from Aconcagua. I have been at 18,000' on Kilimanjaro, the view was absolutely stunning. (But we were tourists, not mountaineers, and had no traction gear. At the time that meant progress became impossible very soon after sunrise. Now the ice has retreated so far that you can expect to summit by daylight without traction gear.)

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.

I think the main insight is that the ocean horizon arrives quite fast.

I see, that's why the longest are peak-to-peak

ok then, If I read you right, what counts is someone going and doing the actual seeing , VS drawing a line on a topigraphical map. there are groups on another quest flying gliders into the high stratospher riding atmospheric waves rolling up against mountains who might also qualify for setting records for the longest possible views through the atmosphear, they got started buying surplus soviet space suits as that was what made attempts possible.

I tried the summit of Mt Ruapehu here in NZ and got 358.8 km to Mt Owen. Not bad as I was expecting Tapuae-o-Uenuku which is a little shorter at 342 km.

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).

Wow, glad you had fun exploring. It suddenly made me think of a little feature that I'm not sure we made the best job of exposing. In the little trophy icon toggle on the right, there's the Top Ten list of views, then under those there's a little line that just says "In current viewport: 123km". Did you see that? Did it make sense? I implemented it, so of course I know that it's better than clicking all the points around a peak to find the longest view from a mountain summit. But maybe it's not obvious to other users? What I do is zoom in so that the viewport only contains the area of the summit (or indeed entire country for that matter) that I'm interested in, then I look at that "In current viewport:" line without having to click anything.

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...

Oh, I missed that!

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)

Right, I think we need to make that "In current viewport" thing more prominent somehow.

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.

> So this is the NZ longest line right

Yup. I'd think so.

> It doesn't always make a difference, but it sometimes can.

I guess the obvious case is if there's a point near one end that is higher, but less than 1.65m higher.

It really might be better to use ground level at both ends. Or at least the same height at both ends e.g. if there is a person on both peaks.

The thing about the observer height that I always try to remember is that features really close to the observer can make an exponential difference. Like imagine how simply putting hand in front of your eyes can suddenly make the whole world disappear. So in theory, it is possible that a mere change of a few centimeters in the height of the observer could affect a similarly dramatic change in the view.

Not a geologist, but interesting that many of these sites are close to equator. Suppose that's where mountains are higher because tectonic plates are more active?

Anyone with expertise want to comment?

Not a geologist either but an astronomer. Never heard that tectonic activity has any association with proximity to equator.

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.

It's also interesting because the radius of curvature is smaller, meaning the distance to the horizon is shorter north south, and a lot of these views are north south. So the increase in mountain height more than overcomes the other effect!

Woah, I've been thinking about this whole project for so long, but never considered that!

Are we saying line of sights are not symmetric? Why not?

The earth is an oblate spheroid to an approximation. It's not that they're not symmetric, but at the equator the north south axis has higher rates of curvature than anywhere else (but the east west has somewhat lower rates because of the larger circumference due to the bulge).

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!

While Everest (8849m) is the highest point above Sea Level, Chimborazo (6267m) in Ecuador is further from the centre of the Earth (about 2000 metres further), due to the equatorial bulge. It's very measurable.

Well that's not what the claim and clarification was about. The question was: can a mountain rise higher in the equator as compared to higher latitudes?

It is not about highest point from centre of Earth. That's is related to equatorial bulge but irrelevant to the discussion.

Hi Tom it's Marc, I'm glad to see you finished your sightline project ! Any clue why you report the longest sightline as "530.8 km" when it seems to be actually 538.1 km? That's what my code calculated (https://news.ycombinator.com/item?id=45512970) that's what Dr. Ulrich Deuschle also calculates (https://www.udeuschle.de/panoramas/panqueryfull.aspx?mode=ne...) You, Deuschle, and I all use the same DEM data (https://www.viewfinderpanoramas.org/Coverage%20map%20viewfin...) and the same refraction coeff (0.13), and nearly the same camera height (1.5m for me, 2.0m for Deuschle, and 1.65m for you—and these differing heights make no difference given the coarse DEM resolution). Something must be slighly off in your computations? Or do you think both Deuschle and I are wrong?

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

Hey Marc, Ryan here. Tom may respond as well

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

Ok that makes sense, thanks for the reply! Maybe document this "percent or so" error in the FAQ since it is about 16 times bigger than the (other?) ~0.0685% error you mention that can be caused by the AEQD reprojections.

Good idea, I'll add it to the FAQ later today. Under a section of "why don't these results match the other tools". The projection error is separate as you mentioned.

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.

Reply to my edit #2: I realize the "To" point 41.0181,77.6708 is just the coordinate of the center of the 1°-wide horizon line. The actual farthest visible point according to your analysis is probably this peak in the west half of the 1° field of view: 41.014862, 77.647818 So I retract my comment about the error being "clearly" on your side. However this does indicate that we definitely calculate things differently. In my analysis Pik Dankova at 41.059542, 77.684808 which is a few km further can actually be seen and that's the source of our differences. I don't know who is right.

It sounds like we're just not casting enough rays then.

Ok! Ping me when you get it updated - I am very curious :-)

Sure!

Hey Marc!

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.

Is this a hobby lots of people have or something? And if so, what is it called? Cartography? I'm surprised to see folks debating this.

I suppose our hobby is related to the hobby of ground-to-ground long-distance observation. Except we don't perform the actual observation, just the math of where it is theoretically feasible :-) In my case, years ago, I did exactly the same as Tom and Ryan: I algorithmically searched for the longest sightline. It was a weekend project just to satisfy my curiosity. Then last year, Tom and I kinda connected informally over this hobby.

Fascinating, I'd never even thought of the longest sightline till now! Well cheers to you and Tom and Ryan, a thoughtful and smart bunch!! :)

The website claims the longest line of sight in my city is 24.7km from someone's garden that is surrounded by houses. I walk past this particular spot on my way to the gym. I walk downhill from my house to get there. I seriously question the reliability of this data.

The resolution of the underlying data is only ~100m. So most houses, vegetation, etc, gets blurred into the same smooth surface. There are actually higher resolution data sets, even up to centimetre scale, using LiDAR, of cities. We'd love to integrate these but it's a few orders of magnitude more data.

I think you're assuming more fidelity than the project is claiming

I'm assuming that when the project says you can see 24 km from a given location, that you can see 24 km from that location. That's not the case. Fundamentally, it doesn't do what it claims to do.

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.

Surely you understand it's based on limited resolution data, and therefore intended to be used at the scale of general topography like mountains and valleys?

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.

Why not complain that there's a point inside somebody's basement and you can't see any distance from that? Why not complain that it's wrong any time you close your eyes? Those would be about as sensible.

Ironically, the site would probably say you can see 20 km from inside the basement.

What's ironic about that? Of course it would. It's working off of large-scale terrain features, not structures. It will also tell you that you can see distant mountains when it's cloudy or you don't have your glasses on.

Now we just need to put two hams with 2m/70cm radios to make the longest line-of-sight QSO on the planet. Bonus points for QRP.

Definitions:

* Hams: Amateur radio operators.

* QSO: conversation or contact between two radio stations.

* QRP: Low power, typically under 5 watts.

That's actually one of the legitimate uses cases we've consider for the algorithm.

This is so rad! Here's a photo of me making a 1.2Ghz FM contact 244km away from the summit of a 14er to the summit of another 14er here in Colorado. That particular band is very line-of-sight, with not much propagation or reflections like even 2m SSB or the HF bands. This is a very fun tool that I can't wait to explore more!

https://www.k0nr.com/wordpress/2021/08/using-1-2-ghz-in-the-...

244km! Oh wow, I never knew people did this kind of thing. Yeah this is exactly the sort of thing we want people to use the app for.

Neat. I did a related project a little while ago. I wasn't interested in how far I can see from everywhere, so much as what I can see from one place in particular.

So in mine you can click on a spot and it draws black lines over any land that is occluded by terrain, within 100km.

(But all with AI-generated JavaScript, not cool Rust and SIMD stuff)

https://incoherency.co.uk/line-of-sight-map/

I am not sure if I'm experiencing what you describe. I just see a radiating circle of black lines, no matter where I click. I decided to click a local, notable "long line" viewpoint -- Lick Observatory outside San Jose. From here, on a clear day, you can see Half Dome in Yosemite, 120mi away. I still just see a black circle.

Are you standing on a raised platform when you see the Half Dome?

This is what I get when I set the observer height to 20m, and increase the "max distance" to 300km (200km = ~124 miles so may not be enough).

https://img.incoherency.co.uk/6478

It's also possible that the half dome is too short and the sampling rate of the line-of-sight jumps over it!

It seems that sometimes it fails to load the height map, try reloading the page. You should see terrain shading if it's loaded properly.

I think the lines indicate areas that you can't see?

It's buggy. Mission peak shows much of the bay area occluded.

> But all with AI-generated JavaScript, not cool Rust and SIMD stuff

Heh, I almost hit back at the "in Rust" mention.

Would the end result have been different if it were done in python calling C libraries for performance? I strongly doubt it.

Isn't cross language function calling expensive? I assume it is significant.

"Viewsheds" of any location can be calculated and matched with photographs using "GeoImageViewer", an application I wrote a couple of years ago. Any feature in the photo can be interactively identified in a mapview and vice versa, including the boundary of the viewshed. See the link below for a couple of examples.

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.

https://hdersch.github.io/Viewing.html

Oh hey, I remember you from the last time I posted something about our project. That's a great app you have.

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.

Hi! Colombian here. I reviewed the second prediction and believe the tags are incorrect. They should be: Pico Lagos del Congo, Liborina, Antioquia to Pico Cristóbal Colón, Sierra Nevada, Magdalena.

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...

Oye, fui a Colombia un par de veces! Y mi profesora Español era Colombiana.

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?

Yes! I think that might be a more exact title. This is what I mean:

First point: - Mountain: Cerro Lago del Congo (The GPS coords refer to the peak) - Locality: Liborina - State: Antioquia

Second point: - Mountain: Sierra Nevada de Santa Marta (The GPS coords refer to the peak, called Pico Cristóbal Colón) - Locality: Santa Marta - State: Magdalena

Pd. Hope you enjoyed your visit! I think Colombia is beautiful (But hey! I am biased)

Actualicé el website! Es mejor así?

Maybe including an actual picture of the sight would be helpful here?

This has been common feedback today. I hadn't appreciated the appetite for photos, but of course it makes sense. I think what we'll try to do is automate linking to some other tool that can produce a 3D panorama, like Google Earth for example.

Great work and thanks for the write up.

Sorry to be pedantic, your longest view is not from the Hindu Kush, but from the mountains to the south of the Tarim Basin which are the Kunlun mountains.

The Hindu Kush are largely in Afghanistan, but also Pakistan, running in an arc from Kabul to the north east. They aren't in China.

The Hindu Kush range then gives way to the Karakoram, as you cross Kashmir, which is then bordered to the north by the Kunlun which form the arc of the southern Tarim Basin.

I suspect you're just mixing it up with the Hindu Tagh pass, just to the south of the peak your point is looking from. Hindu Tagh seems to be about as good a name as the line-of-sight community has come up with for that peak.

We appreciate the pedantry.

I think I came up with that name from a game of telephone of sources claiming to have the longest line of sight. There's a lot of really random sources on the Internet that mention the line of sight but do not cite the data or analysis. I have seen Hindu Tagh thrown around as well so if it's more accurate we want it there.

Part of our motivations were to stop the game of telephone and become an authoritative source on this stuff.

I'm not much of a geographer, more of a HPC guy.

I have this on the TODO list to update tomorrow.

Agreed, pedantry very much appreciated. Website updated!

Here's a potential bug report, but maybe it comes down to the resolution.

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.

Could you post a link to a view that you think might not be right?

The 5-10 tiles north of the tall peaks.

https://map.alltheviews.world/longest/88.14788327735505_27.7...

https://map.alltheviews.world/longest/88.14711648199943_27.7...

I see, thanks. So my thinking is that overly dark areas to the North are caused by _relatively_ low visibility. The heatmap is actually dynamically generated for every viewport. So I agree that there has to be some amazing view from those North faces, it's just that they are drowned out by the sheer enormity of the views on the South face.

If were to use absolute global values for the heatmap, then the Himalayas would just appear as pure, washed-out white.

Does that make sense?

Would probably be really useful for Amateur Radio enthusiasts making low power long distance contacts using VHF/UHF.

I wonder if air quality/humidity permit actually seeing this far though… That’s a lot more “air” than looking up toward space…

Such a great project! I remember an older image of the french alps taken from the pyrenees, at over 400 km. Found it again here:

https://beyondrange.wordpress.com/2016/08/03/pic-de-finestre...

Observations:

1) Poking around our local peaks I find that the calculation appears granular, it's offering me things I could see from the summit that I could not see from where I clicked.

2) It's offering me one I never even considered looking at (peeking just beside another mountain, the terrain appeared flat, I never realized there was a distant peak there) and one I knew about--and know I have no hope of actually seeing.

1) So you're expecting to click and see a line of sight that you've seen in real life? Is it just that each point only every records the _longest_, which not be the best or most notable view? 2) As in, in a good way?

I've seen Mallorca from the Tibidabo mountain in Barcelona (the website states it is 194km). It required number of attempts for perfect atmosphere.

This is an independent observation from the Fabra Observatory: https://english.elpais.com/elpais/2015/03/03/inenglish/14253...

What would it take to generate visualizations like this automagically?

https://viewfinderpanoramas.org/panoramas/ASIA/EVEREST-SOUTH...

I don't know, but I really want to do it.

Cool places to try wifi long shots.

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

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.

This data base could be used to optimally place meshtastic nodes.

You could just send raw 802.11 data frames and then receive them with monitor mode on the other end.

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.

I think this is the furthest true photography [1] with 443 km distance, into the sunrise (corrected from sunset)

[1] https://beyondrange.wordpress.com/2016/08/03/pic-de-finestre...

The record was actually recently beaten https://www.guinnessworldrecords.com/world-records/66661-lon...

Thanks, didn't knew that and 11% further is quite a increase and not too far from the maximum possible.

What could be causing these large-scale grid lines to show up in the heatmap in Florida?

https://map.alltheviews.world/longest/-83.1653564346176_29.8...

Oh wow, yes, very curious. I believe that is caused by the cleaning of the original NASA data by the creator of https://viewfinderpanoramas.org/dem3.html So whilst they improved the data, it still isn't perfect.

Ultimately we plan to mix in higher resolution data from different more recent surveys.

Oh, neat. I do an amateur radio challenge called SOTA where any peak with 150m prominence is a candidate. British Columbia has detailed LIDAR data so I figure it would be straightforward to do, I just don't know anything about GIS to make it happen. I'll have to browse the repo for some hints.

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.

Thanks, yes this is actually one of the legitimate usecases we hope for from our algorithm.

Since you have the data could you show how far you can see in every direction rather than the longest direction?

Yes, but, there's one small problem, storing this extra data for the whole world starts to run into the petabytes!

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.

Ohh yes, nice ideas.

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.

This would be incredible - please add this!

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.

Could it be this? https://www.udeuschle.de/panoramas/makepanoramas.htm

No, it used a much heavier JS interface and IIRC it also used Google Earth. That is a nice tool, thanks for sharing it.

It was https://caltopo.com/

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

heywhatsthat?

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.

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!

Thank you! This is exactly the kind of thing I was hoping people would use this for.

You can see Scotland from Wales! https://map.alltheviews.world/longest/-3.9754324057705617_53...

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.

I was in Kyrgyzstan last year and saw some distant mountains that I was able to work out were in Kazakhstan, over 100km away. Even that felt pretty amazing at the time.

500km? Whee...

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

I was expecting photos...

Here's a not bad (and accidental!) 342 km one from 7 months ago:

https://www.reddit.com/r/newzealand/comments/1m9p0bh/tapuaeo...

In theory there should be a 365.3 km one just barely to the left of the obvious twin peaks, but I'm not seeing it.

Quite a bit short of the longest in the world, but still pretty far to see.

Related: https://news.ycombinator.com/item?id=34609865

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?

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.

Exactly.

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

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.

This will be useful in the laser wars.

Hopefully this won't become a tool for the Flat Earthers. =)

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.

We're actually thinking of writing a SIGBOVIK paper where we explore running this whole thing for a Flat Earth!

The ham radio microwave community thanks you.

This is the geography I was promised in school

Can you actually see anything in real life though?

The longest and second longest haven't been photographed yet, but #3 has https://www.guinnessworldrecords.com/world-records/66661-lon...

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?

The AEQD projection radiates from the anchor right? Is that what you mean by polar coordinates? This was my first foray into optimising projections so if you have any insight I'd love to learn.

If you know anything about QGIS plugins please feel free to make a brief write up in our issues https://github.com/AllTheLines/viewview/issues

I just mean that you only need it evaluated at the points along the azimuths you consider, but maybe that doesn't make sense computationally and it's faster to interpolate from a grid anyway.

I might create an issue after I conceptualize what it might look like more!

this is very cool, but i want to see photos!

Thanks for confirming this! I read the speculation, and traveled fairly close to Dankova. Actually climbing it is a serious land expedition from the nearest international airport.

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.

Isn't there a curved photonic beam method that technically, in space, can send a photon around the world at least once?

Airy beams curve

This type of amplification preserves the curvature of Airy beams FWIU:

"Low-power integrated optical amplification through second-harmonic resonance" (2026) https://news.ycombinator.com/item?id=46824978

What kinds of sensing would be possible given a round-the-world photon trajectory?

Quasiparticles have mass, and so might be easier to send around the world than purportedly massless photons.

SQR Superfluid Quantum Relativity with a dilatant fluid says that the effects of mass energy equivalence at high velocities approaching c are actually due to the (atmospheric to superfluiic) viscosity of spacetime nonlinearly pushing back.

But does that matter for a photon or a massless quasi-particle like a photon that we're trying to curve initially to send around the earth at least once to win teh line of sight distance ranking?

There is a theory that the star shafts of the Great Pyramid could have been used as waveguides. They did contain copper rods. Perhaps they were just lightning rods.

If so, then the pyramids (and other ancient megalithic structures with quartz at 72 degree intervals) and Angkor Wat and Longyou caves and Osireon may have been the longest (non-) line of sight communication system back then in ancient times: https://gemini.google.com/share/101970a04402

Observation of a salt-formed Hydrogen-tuned NV-center diamond might resolve some of these claims?

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?

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/).

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.

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.

It's a sort of high-pass filter I guess? Using the curvature of the earth to highlight local changes in elevation.

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.

This is my favourite kind of HN post, and I absolutely love this one. Would love to see photos from each of these views.

Thank you <3

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

I was looking for those on the website. Maybe we could find some photos on Google Maps that already exist from these locations.

It be nice to get the 3 or 5 longest distances from a specific point, not just the longestest

It's just a matter of storage costs. Even storing a single line of sight for every point on the planet is over 200GB!

Claps!

Thanks umpriel for the PR, hope you're well!

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