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Technique for Manipulating Satellite Photos Now Reveals Ancient Images (2025)
https://dstretch.com/DecorrelationStretch.pdf https://dstretch.com/DecorrelationStretch.pdf
https://www.nasa.gov/technology/tech-transfer-spinoffs/nasa-technique-for-manipulating-satellite-photos-now-reveals-ancient-images/ https://www.nasa.gov/technology/tech-transfer-spinoffs/nasa-...
- NDlurker 23d agoAmazing. This will change how I take photos
- Aboutplants 23d agoGoing to be taking a lot more pictures of rock faces!
- NDlurker 23d agoI want to try this on faded graffiti. I have a few spots in mind already.
- tedecristal 23d agoany repo or link where other people can try?
- ortusdux 23d agoMatlab - https://www.mathworks.com/help/images/enhance-color-separation-using-decorrelation-stretching.html https://www.mathworks.com/help/images/enhance-color-separati... This paper might also be of interest - https://www.mdpi.com/2227-7390/13/20/3297 https://www.mdpi.com/2227-7390/13/20/3297 "In this paper, we review the theory behind decorrelation stretch and propose some alternative algorithms that resolve the issues of the standard approach."
- pimlottc 23d agoThe app is called DStretch, it's available for iOS and Android https://dstretch.com/Apps/index.html https://dstretch.com/Apps/index.html
- Aboutplants 23d agoSomeone needs to vibecode some updated options
- mightysashiman 23d agoThat isn't 20 bucks. Seriously, this is crazy pricing for an app.
- tyrabound 23d agoAny would you not want to support someone who implanted this? You probably squander more than $20 on meaningless nonsense frequently, why not support him a bit?
- Aboutplants 23d agoBecause at $20 it’s cost prohibitive to a lot of non-professionals who may want to go out exploring and potentially find new discoveries. The app is also a 7 years old
- ButlerianJihad 23d ago"A contribution is mandatory before I will send the plugin. It may take me a few days to respond, have patience. Please note that the plugin is not an app. It has much more functionality than is possible in an app on a smartphone." "The DStretch [mobile] app is a lightweight version of DStretch intended to give users the ability to enhance rock art in the field. It is not a substitute for the DStretch plugin which has much more functionality."
- shannietron 23d agoHad an llm build something quickly so I could play with it. https://shannietron.github.io/decorrelation_stretch/ https://shannietron.github.io/decorrelation_stretch/
- hackyhacky 23d agoYou the real MVP
- marcd35 22d agothis is awesome. can you open source it so i can fork it and add some enhancements like exposure/contrast adjustments etc?
- shannietron 22d agoit is already open sourced, https://github.com/shannietron/decorrelation_stretch https://github.com/shannietron/decorrelation_stretch
- yread 23d agoThere is also a 21 euro app https://play.google.com/store/apps/details?id=com.dstretch.androiddstretch https://play.google.com/store/apps/details?id=com.dstretch.a...
- EQFitzgerald 23d agoThis supports something similar (PCA color stretch) https://meesoft.com/Analyzer/ https://meesoft.com/Analyzer/
- pimlottc 23d agoThis is based off a NASA article, which has an expanded version with more details here: https://spinoff.nasa.gov/Manipulating_Satellite_Photos_Now_Reveals_Ancient_Images https://spinoff.nasa.gov/Manipulating_Satellite_Photos_Now_R...
- homeonthemtn 23d agoWay better, thank you
- yorwba 23d agoThe 1996 paper mentioned in the NASA article: https://dstretch.com/DecorrelationStretch.pdf https://dstretch.com/DecorrelationStretch.pdf
- euroderf 23d agoTFA is lossy compression ?
- tomhow 23d agoUpdated from https://gizmodo.com/this-nasa-color-trick-was-meant-for-mars-now-its-unveiling-rock-art-on-earth-2000809844 https://gizmodo.com/this-nasa-color-trick-was-meant-for-mars..., thanks!
- cwmoore 23d ago[flagged]
- HPsquared 23d agoSee also: Eulerian Video Magnification (EVM) to amplify subtle motions and colour changes: https://youtu.be/ONZcjs1Pjmk https://youtu.be/ONZcjs1Pjmk https://youtu.be/_qtzWNZApsw https://youtu.be/_qtzWNZApsw
- roger_ 23d agoAlways wanted to implement that on a phone, it would be like a superpower!
- NegativeLatency 22d agoSucks that they patented it https://patents.google.com/patent/US9338331B2/en https://patents.google.com/patent/US9338331B2/en
- dylan604 23d ago“No one really knows why people made the rock art they made, at least in many cases,” Harman said Well, it's obvious they really wanted to though. This isn't like marking on a wall with a Sharpie. They had to work at it to make it happen. The commitment alone is impressive even if it was just a "Grogg was here!"
- Terr_ 23d agohttps://smbc-comics.com/comic/rite-on https://smbc-comics.com/comic/rite-on > "No matter what you do, when we find something weird in ancient history we will decide it must've been part of a fertility rite."
- tyrabound 23d agoDecently intentional and deliberate in many if not most cases. There are examples of it in high up places along sheer cliff walls in Arizona that boggle the mind trying to figure out how they managed to accomplish it and at the scale they are, then there are cave paintings that are hundreds of meters deep inside narrow caves in Europe. It actually makes me wonder if this technique would produce any results in the notorious Erdstalls in Germany. I suspect not, but no one has any better ideas, so it might be worth checking.
- fc417fc802 22d ago> the notorious Erdstalls It seems quite strange that they could be that prolific while requiring that much manual labor to construct yet there's no written reference to any of them.
- matja 23d agoYou can do something similar in GIMP: 1) Colors > Components > Decompose > LAB 2) For the layers of the A/B (chroma) channels, Colors > Levels > "Auto Input Levels" (maximize the contrast), and move the mid point to the median. 3) Colors > Components > Compose > LAB
- MisterTea 23d agoCan you explain 2 a bit more? I see the Auto input levels but unsure what you mean by "move the midpoint to the median." The result I got for the original mars image was a washed out red image with some yellow around the craters.
- matja 23d agoThe levels tool maps a subset of the channel range to the full range, effectively changing the brightness and contrast in one step. The center point controls the gamma correction, so you can map a biased distribution (mostly bright or dark for example) to be more evenly distributed. That was the purpose of that step - move the midpoint slider to about where the peak in the histogram is, to get an evenly distributed range. The low/high slider can be moved towards that to increase the contrast. "Contrast" here will only apply to the A/B channels, which is the color information, so it's increasing the color contrast and unbiasing it, while keeping the luminance information. Photoshop also can do the same transform, and interactively in the LAB colorspace (no need to combine/uncombine the channels first).
- MisterTea 23d agoThanks for the details but I realized I should have said "Pretend I just installed GIMP and my knowledge of image editing is MS paint." This is what I was after: "move the midpoint slider to about where the peak in the histogram is, to get an evenly distributed range." It kinda worked! Thank you and sorry for making you explain the gory details though they are appreciated and useful.
- zamadatix 23d agoI interpreted that step as "once you click 'Auto Input Levels', drag the center triangle of the 3 at the bottom of the histogram to where you think the median of the histogram is". That middle slider defaults to being the midpoint of the other 2 sliders. I'm not sure if there is a smarter way to move it to the median beyond "looks about right". I got this as a result https://i.imgur.com/RsXx3y2.jpeg https://i.imgur.com/RsXx3y2.jpeg and it certainly doesn't preserve the color of the rest of the image (there are probably more algorithmic steps needed for that) but it does seem to make highlight the same faint patterns much more clearly.
- mlmonkey 23d agoIs there an imagemagick implementation that I can just throw into the pipeline?
- xd1936 23d ago[flagged]
- timschmidt 23d agoWeather satellites have done more to increase crop yield than anything since the invention of artificial fertilizer and save more lives.
- qurren 23d agoI tried to look for hidden rock art at Ankgor Wat by imaging with multiple bandpass filters and amplifying cross-spectral differences. I didn't succeed, but maybe I was in the wrong place. The shit guards there also didn't like me using a tripod while I changed filters, so it was also hasty.
- blincoln 23d agoIf it makes you feel any better, I've also never had any luck finding hidden rock art, petroglyphs, or similar using multispectal bandpass filters or decorellation stretching. I was super excited about DCS based on some of the recovered petroglyph photos online, and integrated it into some software I wrote years ago.[1] Still hoping I find something as interesting with it as the fellow mentioned in the article. It works, but I haven't had a "gosh, I never would have seen that without DCS!" moment. [1] https://www.beneaththewaves.net/Photography/Decorrelation_Stretch_Images.html https://www.beneaththewaves.net/Photography/Decorrelation_St... / https://www.beneaththewaves.net/Software/The_Mirrors_Surface_Breaks.html https://www.beneaththewaves.net/Software/The_Mirrors_Surface...
- wdutch 23d agoSounds like they were the opposite of shit if they noticed someone setting up specialist equipment. I don't think any national monument in the world would be keen on people doing that without advanced permission.
- qurren 22d agoYou will never get explicit permission unless you have connections. So until that kind of beaurocracy changes, this is the kind of thing you just go ahead and do. Life is short, assuming it is fully non-destructive and leave-no-trace, just do it until someone gets in your way.
- fc417fc802 22d agoAs long as it's equivalent to a camera on a tripod, why not? Outside of impeding traffic flow or museums that want to charge you for it being bothered by that seems entirely counterproductive.
- 1shooner 23d agoDStretch is also really great at revealing painted ghost signs on old buildings.
- Waterluvian 23d agoFalse colour composites were something I was introduced to in high school GIS and did a lot of in undergrad remote sensing. It was one of those Eureka! moments for me in terms of developing a better understanding of signals and signal processing, as well as sensors and data collection. Ie. absorbing the reality that the way in which my eyes (or any optical sensor) see the world is not canonical. Vegetation is red, not green! It was also just the COOLEST THING EVER to swap infrared bands in LANDSAT ETM+ imagery and watch vegetation immediately pop out at you. It's what turned this sort of dull (at least for a teenager) geoscience into a kind of puzzle where you have to figure out how to bring the signal up out of the data.
- jacobolus 23d agoIt's really fun to play with black and white photography using various kinds of color filters and see how different you can get the same scene to appear. (Also fun to play with a polarizing filter.)
- dylan604 23d agoin the same vein, most high-end astrophotography imagers use B&W CCD sensors. Instead of dividing the pixel count by the RGBG layout, you get the full sensor worth of pixels. Different filters are used and then recombined using false color merging. Also, high-end motion film scanners using B&W CCD sensors using RGB filters so that each frame of film is scanned 3 times.
- adolph 22d agoThis done to enhance light gathering, right? Normal color CCDs have per-pixel filters so lose some light in order to gather the light at the same time? The most common method is to blanket the CCD pixel array with an alternating mask of red, green, and blue (RGB) microlens filters arranged in a specific pattern, usually the Bayer mosaic pattern. https://www.microscopyu.com/digital-imaging/introduction-to-charge-coupled-devices-ccds https://www.microscopyu.com/digital-imaging/introduction-to-...
- freetime2 23d agoMy first thought reading this headline was "Really? Nobody thought of this until now?" But reading further, the Dstretch plugin has been around since 2005 or so. And presumably people have been using contrast enhancement, color manipulation, multispectral imaging, etc. to uncover hidden images long before that. So not exactly "news" at this point. But still a pretty cool success story. It almost feels like a feature that should be built into the default camera app. For anyone wanting to conduct their own forensic analysis to determine how thoroughly their hotel room has been cleaned, for example (although personally I'd probably rather not know).
- deleted 23d ago[deleted]
- fc417fc802 22d ago> For anyone wanting to conduct their own forensic analysis to determine how thoroughly their hotel room has been cleaned, for example Probably more effective to bring a UV flashlight with you.
- rf15 23d agoI'm surprised this is getting so much coverage; This is well known from medical imagining and whatnot, that you take a black&white/limited gamut space and spread it to the full perceivable gamut.
- BlackRabbit1 23d agoVery Cool! I have a lot of 40MPx RAW pictures from the almost unreadable historic written walls in Delphi, Greece. Let me test this with them.
- NegativeLatency 22d agoHow'd it turn out?
- BlackRabbit1 22d agoI played around with the LLM-Generated website (see past posts here) of this algorithm and the Gimp method. It actually doesn't improve the readability of the letters carved in stone nor does it show any hidden details on the surroundings (at least in my very small amount of pictures). But that's not unexpected as they readability depends on the angle of light and shadow. I have to look into my archives.. maybe there are some wall paintings on which this kind of algorithms excels. Surprisingly it's working very good in finding living plants and separating it from hay.
- macmac 23d ago>But it’s also due to the chance intersection of one man’s hobby with his unrelated professional and educational background. I wonder how many great inventions can be traced to this type of circumstances. I suspect more than we realize.
- bookofjoe 22d agoI loved reading this comment stream even though I understood nothing about the technical aspects involved: rather, it's the lack of hostility and aggressiveness as opposed to the enthusiastic and welcoming attitude of almost all commenters, so rare in these threads here nowadays.
- tomrod 22d agoHacker News is genuinely one of the few communities that seems to improve as it ages and grows. Somehow, despite strong concerns about an eternal September, it seems to say "Hey, come in and lets learn together." I just think its neat.
- zamber 22d agoI made a quick vibe-coded on-device web app trying to replicate what dstretch does: https://zamber.github.io/dstretch/index.html https://zamber.github.io/dstretch/index.html
- alexpotato 22d agoSome books, from off the top of my head, that use interesting color film processing or other "photographs saw something humans can't: - The Sunbird by Wilbur Smith [0] IIRC, archaeologists use side lighting and IR film + lenses to identify that a stone wall was made out of bricks and then painted over. This hid an entrance to a special place (don't want to spoil too much). - Congo by Michael Crichton [1] The protagonists use a camera + satellite link to visually scan a mural and then send the scan back to supercomputers for processing. That mural explains a key point about the jungle where the humans find themselves. Earlier in the story, I believe the one character analyses chromatographic images of jungle canopies to find where the ancient city might be. Both books are from the 1970s/1980s so fascinating to see this happen using modern technology too. I would curious if folks are aware of other books where photographic analysis plays a part. 0 - https://amzn.to/4gZFoUW https://amzn.to/4gZFoUW 1 - https://amzn.to/4gLBsbI https://amzn.to/4gLBsbI