[HN Gopher] Show HN: Algorithmically finding the longest line of...
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Show HN: Algorithmically finding the longest line of sight on Earth
We're Tom and Ryan and we teamed up to build an algorithm with Rust
and SIMD to exhaustively search for the longest line of sight on
the planet. We can confirm that a previously speculated view
between Pik Dankova in Kyrgyzstan and the Hindu Kush in China is
indeed the longest, at 530km. We go into all the details at
https://alltheviews.world And there's an interactive map with over
1 billion longest lines, covering the whole world at
https://map.alltheviews.world Just click on any point and it'll
load its longest line of sight. Some of you may remember Tom's
post[1] from a few months ago about how to efficiently pack
visibility tiles for computing the entire planet. Well now it's
done. The compute run itself took 100s of AMD Turin cores, 100s of
GBs of RAM, a few TBs of disk and 2 days of constant runtime on
multiple machines. If you are interested in the technical details,
Ryan and I have written extensively about the algorithm and
pipeline that got us here: * Tom's blog post:
https://tombh.co.uk/longest-line-of-sight * Ryan's technical
breakdown: https://ryan.berge.rs/posts/total-viewshed-algorithm
This was a labor of love and we hope it inspires you both
technically and naturally, to get you out seeing some of these vast
views for yourselves! 1.
https://news.ycombinator.com/item?id=45485227
Author : tombh
Score : 353 points
Date : 2026-02-09 10:05 UTC (12 hours ago)
(HTM) web link (alltheviews.world)
(TXT) w3m dump (alltheviews.world)
| umpriel wrote:
| Claps!
| ryanbberger wrote:
| Thanks umpriel for the PR, hope you're well!
| zoobab wrote:
| Cool places to try wifi long shots.
|
| I did some longshots back in the early days of wifi.
| ErroneousBosh wrote:
| You'd need to do a bit of work to adjust the timing, I suspect.
| At 530km the time delay would be around 1.75ms which would be
| enough to greatly upset WiFi ;-)
|
| You could probably talk between ends using cheap crappy 446MHz
| 250mW walkie-talkies though.
| galangalalgol wrote:
| This data base could be used to optimally place meshtastic
| nodes.
| 1e1a wrote:
| You could just send raw 802.11 data frames and then receive
| them with monitor mode on the other end.
| ErroneousBosh wrote:
| 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.
| jstanley wrote:
| 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/
| eitally wrote:
| 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.
| arethuza wrote:
| I think the lines indicate areas that you _can 't_ see?
| jychang wrote:
| It's buggy. Mission peak shows much of the bay area
| occluded.
| jstanley wrote:
| 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!
| 1e1a wrote:
| 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.
| nottorp wrote:
| > 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.
| spookie wrote:
| Isn't cross language function calling expensive? I assume it
| is significant.
| rob74 wrote:
| 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?
| tombh wrote:
| 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.
| rob74 wrote:
| 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 -12degC 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...
| codethief wrote:
| > 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.
| ofrzeta wrote:
| 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 Fohn 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%C
| 3%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.
| ColinEberhardt wrote:
| > 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
| ;-)
| tombh wrote:
| Roy Castle!
| ColinEberhardt wrote:
| Bingo! Loved that show
| avisser wrote:
| 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.
| bratbag wrote:
| Its a really interesting question.
|
| Lets take it to its farthest extent: can you take a
| picture of a black hole?
| tshaddox wrote:
| Or how about this: can you take a photograph of a shadow?
| tshaddox wrote:
| 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.
| metalman wrote:
| 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.
| ja-mf wrote:
| 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/
| CGMthrowaway wrote:
| 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
| allan_s wrote:
| I think the main insight is that the ocean horizon arrives
| quite fast.
| CGMthrowaway wrote:
| I see, that's why the longest are peak-to-peak
| LorenPechtel wrote:
| 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.
| danielsamuels wrote:
| 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.
| tombh wrote:
| 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.
| DiggyJohnson wrote:
| I think you're assuming more fidelity than the project is
| claiming
| danielsamuels wrote:
| 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.
| crazygringo wrote:
| 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.
| wat10000 wrote:
| 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.
| danielsamuels wrote:
| Ironically, the site would probably say you can see 20 km
| from inside the basement.
| wat10000 wrote:
| 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.
| brucehoult wrote:
| 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).
| repelsteeltje wrote:
| 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?
| kmaitreys wrote:
| 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.
| jmalicki wrote:
| 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!
| tombh wrote:
| Woah, I've been thinking about this whole project for so
| long, but never considered that!
| rao-v wrote:
| Are we saying line of sights are not symmetric? Why not?
| jmalicki wrote:
| 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!
| iso1631 wrote:
| 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.
| kmaitreys wrote:
| 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.
| tombh wrote:
| 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...
| brucehoult wrote:
| 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)
| tombh wrote:
| 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.alltheview
| s.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.
| alvsilvao wrote:
| 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
| ourmandave wrote:
| Hopefully this won't become a tool for the Flat Earthers. =)
| emiliobumachar wrote:
| 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.
| tombh wrote:
| We're actually thinking of writing a SIGBOVIK paper where we
| explore running this whole thing for a Flat Earth!
| pestatije wrote:
| It be nice to get the 3 or 5 longest distances from a specific
| point, not just the longestest
| noosphr wrote:
| Since you have the data could you show how far you can see in
| every direction rather than the longest direction?
| bartread wrote:
| This would be incredible - please add this!
| tombh wrote:
| Yes, but, there's one small problem, storing this extra data
| for the whole world starts to run into the petabytes!
| em-bee wrote:
| what if you put a limit on it? like only a dozen views per
| point, and only views that are at least 100km. or only do
| this for peaks or points of interest. or some combination
| like more views for higher peaks, less for lower ones.
| tombh wrote:
| Ohh yes, nice ideas.
| em-bee wrote:
| 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.
| drcongo wrote:
| This is my favourite kind of HN post, and I absolutely love this
| one. Would love to see photos from each of these views.
| tombh wrote:
| Thank you <3
|
| Well there is a photo near our #3 longest line of sight
| https://www.guinnessworldrecords.com/world-records/66661-lon...
| venusenvy47 wrote:
| I was looking for those on the website. Maybe we could find
| some photos on Google Maps that already exist from these
| locations.
| em-bee wrote:
| 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?
| laci37 wrote:
| 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.
| tombh wrote:
| Exactly.
|
| And it could even be tweaked slightly with some favourable
| refraction.
| stockresearcher wrote:
| 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.
| alansaber wrote:
| This is the geography I was promised in school
| 1970-01-01 wrote:
| There was a post here about 6 years ago for a site that
| calculated line of site for any two points on a map with both the
| max line of sight and 2D cross sectional view of the terrain
| difference between the two points. I haven't been able to find it
| since 2020, but it was awesome.
| tombh wrote:
| Could it be this?
| https://www.udeuschle.de/panoramas/makepanoramas.htm
| 1970-01-01 wrote:
| No, it used a much heavier JS interface and IIRC it also used
| Google Earth. That is a nice tool, thanks for sharing it.
| sandos wrote:
| heywhatsthat?
| 1970-01-01 wrote:
| 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.
| 1970-01-01 wrote:
| It was https://caltopo.com/
|
| https://www.heywhatsthat.com/ is another bookmark that I had
| lost to time.
| colechristensen wrote:
| 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.
| tombh wrote:
| 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.
| colechristensen wrote:
| It's a sort of high-pass filter I guess? Using the curvature
| of the earth to highlight local changes in elevation.
| tombh wrote:
| 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.
| sandos wrote:
| 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.
| mrb wrote:
| 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
| ryanbberger wrote:
| 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
| mrb wrote:
| 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.
| ryanbberger wrote:
| 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.
| tombh wrote:
| 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.
| mrb wrote:
| Reply to my edit #2: I realize the "To" point 41.0181,77.6708
| is just the coordinate of the center of the 1deg-wide horizon
| line. The actual farthest visible point according to your
| analysis is probably this peak in the west half of the 1deg
| 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.
| tombh wrote:
| It sounds like we're just not casting enough rays then.
| IshKebab wrote:
| Can you actually see anything in real life though?
| tombh wrote:
| The longest and second longest haven't been photographed yet,
| but #3 has https://www.guinnessworldrecords.com/world-
| records/66661-lon...
| amingilani wrote:
| 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.
| tombh wrote:
| That's actually one of the legitimate uses cases we've consider
| for the algorithm.
| stilldavid wrote:
| 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-...
| tombh wrote:
| 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.
| hybrid_study wrote:
| Maybe including an actual picture of the sight would be helpful
| here?
| tombh wrote:
| 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.
| justjash wrote:
| Pretty interesting. I recently got some cheap Meshtastic devices
| just to play around with and it looks like the longest line of
| sight from my house is about 20 miles. Might have to leave one at
| home and see if I can directly connect to it from the general
| area it is showing.
| tombh wrote:
| Thanks, yes this is actually one of the legitimate usecases we
| hope for from our algorithm.
| __mharrison__ wrote:
| I was expecting photos...
| crazygringo wrote:
| 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...
| mrb wrote:
| 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).
| tombh wrote:
| 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
| rrrpdx1 wrote:
| 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?
| tombh wrote:
| 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?
| rrrpdx1 wrote:
| 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.
| tombh wrote:
| 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.
| LorenPechtel wrote:
| 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.)
| crazygringo wrote:
| 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.
| tombh wrote:
| 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?
| stevage wrote:
| Also spell out what "line of sight" means in this context.
| shric wrote:
| 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.
| stevage wrote:
| Yes, I worked it out - just a suggestion for making the
| article better.
| werds wrote:
| You can see Scotland from Wales!
| https://map.alltheviews.world/longest/-3.9754324057705617_53...
| tombh wrote:
| 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.
| observationist wrote:
| I found my big summer hike. It's the farthest point that can be
| seen from the highest point near where I live. I can make the
| hike and then get some pictures of that highest point, from the
| farthest point away it has a line of sight.
|
| Thanks for this tool!
| tombh wrote:
| Thank you! This is exactly the kind of thing I was hoping
| people would use this for.
| comonoid wrote:
| 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...
| croisillon wrote:
| Related: https://news.ycombinator.com/item?id=34609865
| keepamovin wrote:
| 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?
| lutusp wrote:
| 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/).
| hdersch wrote:
| "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
| tombh wrote:
| 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.
| _whiteCaps_ wrote:
| 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.
| sllabres wrote:
| 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...
| tombh wrote:
| The record was actually recently beaten
| https://www.guinnessworldrecords.com/world-records/66661-lon...
| sllabres wrote:
| Thanks, didn't knew that and 11% further is quite a increase
| and not too far from the maximum possible.
| kawfey wrote:
| The ham radio microwave community thanks you.
| gfarah wrote:
| 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 Cristobal Colon, Sierra Nevada,
| Magdalena.
|
| Additionally, the GPS coordinates might need adjustment, as there
| are several prominent peaks near both Liborina and Pico Cristobal
| Colon (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...
| tombh wrote:
| Oye, fui a Colombia un par de veces! Y mi profesora Espanol era
| Colombiana.
|
| So you're saying a better title for the Colombian line of sight
| could be "Pico Lagos del Congo to Pico Cristobal Colon"? 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?
| LorenPechtel wrote:
| 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.
| tombh wrote:
| 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?
| cvoss wrote:
| 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...
| tombh wrote:
| 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.
| fooker wrote:
| 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.
| tombh wrote:
| Could you post a link to a view that you think might not be
| right?
| fooker wrote:
| 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.
| ..
| 12ian34 wrote:
| this is very cool, but i want to see photos!
| stevage wrote:
| 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...
| cozzyd wrote:
| 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?
| fooker wrote:
| What would it take to generate visualizations like this
| automagically?
|
| https://viewfinderpanoramas.org/panoramas/ASIA/EVEREST-SOUTH...
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