A NASA Color Trick for Mars Is Now Revealing Ancient Rock Art on Earth
NASA Color Trick Was Meant for Mars. Now It's Unveiling Rock Art on Earth
In 2005, archaeologist Jon Harman adapted decorrelation stretch—a NASA JPL algorithm from 1978 for enhancing satellite imagery—into the Dstretch plug-in. It has since uncovered faded rock art worldwide: a yellow figure in Baja California, bats and pigs at Beni Hassan in Egypt, over 200 paintings at Angkor Wat, and a horse-and-rider pictograph in Alberta.
I started playing around and found that by changing the color space I was working in, I could get good results in different images.
- pimlottc
This is based off a NASA article, which has an expanded version with more details here:
https://spinoff.nasa.gov/Manipulating_Satellite_Photos_Now_R...
- Waterluvian
False 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.
- matja
You 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
- qurren
I 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.
- dylan604
“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!"