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:
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
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?
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
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?
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.
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!
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
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.
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
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.
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.
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.
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.
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.
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)
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.
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?
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!
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.
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'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.
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)
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.
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.
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.
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/).
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.
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.
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.
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.
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?
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.
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.
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.
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.
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.
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 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!
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
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.
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
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.
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.
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.
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.
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.
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!
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.
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.
Maybe including an actual picture of the sight would be helpful here?
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...
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.
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.
Related: https://news.ycombinator.com/item?id=34609865
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.
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.
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.
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/).
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.
It was https://caltopo.com/
https://www.heywhatsthat.com/ is another bookmark that I had lost to time.
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.
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.
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.
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.
This would be incredible - please add this!
I was expecting photos...
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
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?
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...
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 is the geography I was promised in school
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!
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.
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
Claps!
Thanks umpriel for the PR, hope you're well!