Technique for Manipulating Satellite Photos Now Reveals Ancient Images (2025)
spinoff.nasa.gov
spinoff.nasa.gov
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.
(Also fun to play with a polarizing filter.)
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.
Pretty funny to figure out that your perspective wasn't objective reality and then immediately decide to canonicalize another arbitrary reality as the One True Reality.
As an old guy, this is something I'm jealous of in a positive way. I'm impressed that schools are offering this type of subject. My senior year was the first year to introduce a "computer science" class where I learned PASCAL on an Apple SE/30. The year after I graduated, the school created an actual computer lab. To be honest, I haven't even thought about looking to see what is available in schools today, but nice to hear something positive
My public high school was a "Geography / GIS magnet school" because some unnamed retired geography teacher donated a very large sum to make it happen. I was an underachieving student with no ambitions to go anywhere, doing just enough to pass. The geography program teacher pulled me aside and encouraged me to sign up for Grade 10 GIS the next year. It became my first academic passion and my entire life pivoted.
I studied GIS/remote sensing every year. I participated in Skills Canada a few times, eventually going the full distance by winning gold at the regional and provincial levels. I was accepted to University for GIS/Remote Sensing. I earned a BES, defended a thesis, earned an MSc, won a national award for GIS, and got into remote sensing + robotics as a career, which I'm still doing ~15 years later.
I don't think I have the words to really describe just how thankful I am for everything teachers and professors did along the way to support and encourage people like me.
At 12 years old, they get an Arduino and start programming in C. Then over the years they do all kinds of interesting things with it: build a car with controlled acceleration, build a tiny house with all kinds of sensors and controllers, monitor algae breeding.
When my son was 16, they brewed their own beer (Hey, it's Belgium and they can legally drink at 16 :D)
Now in the final year, they can propose their own projects. I heard previous years did things like create their own windmill and analyse the efficiency, electric generators in rain drainpipe, etc.
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
The result I got for the original mars image was a washed out red image with some yellow around the craters.
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).
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.
I got this as a result 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.
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).
Probably more effective to bring a UV flashlight with you.
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_St... / https://www.beneaththewaves.net/Software/The_Mirrors_Surface...
Life is short, assuming it is fully non-destructive and leave-no-trace, just do it until someone gets in your way.
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!"
> "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."
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.
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.
- 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.
I wonder how many great inventions can be traced to this type of circumstances. I suspect more than we realize.
Let me test this with them.
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.
This paper might also be of interest - 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."
The app is also a 7 years old
"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."
https://spinoff.nasa.gov/Manipulating_Satellite_Photos_Now_R...