{"id":533650,"date":"2026-09-09T01:15:56","date_gmt":"2026-09-08T15:15:56","guid":{"rendered":"https:\/\/www.nasa.gov\/?p=1041705"},"modified":"2026-09-09T01:15:56","modified_gmt":"2026-09-08T15:15:56","slug":"nasa-technique-for-manipulating-satellite-photos-now-reveals-ancient-images","status":"publish","type":"post","link":"https:\/\/www.vibewire.com.au\/?p=533650","title":{"rendered":"NASA\u00a0Technique for Manipulating Satellite Photos Now Reveals Ancient Images\u00a0\u00a0"},"content":{"rendered":"
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3 min read<\/p>\n

Preparations for Next Moonwalk Simulations Underway (and Underwater)<\/h1>\n<\/div>\n<\/div>\n<\/div>\n
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Jon Harman poses in front of an example of the Rancho Bernardo style of Native American artwork that\u2019s barely visible until Dstretch is applied.\u00a0<\/div>\n
Credit: Jon Harman\u00a0<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

High in the central tower in the ancient Cambodian temple of Angkor Wat, paintings depict horseback riders and a traditional musical ensemble. Thousands of visitors pass these images daily without noticing, because they\u2019re faded to the point of invisibility. <\/p>\n

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They were discovered between 2010 and 2012, along with about 200 other paintings throughout the complex, by an archaeologist using a method conceived at NASA\u2019s Jet Propulsion Laboratory in Southern California. <\/p>\n

The technique, known as decorrelation stretch, heightens contrasts in digital imagery, making features easier to spot. It is especially popular for studying ancient rock art, partly due to the chance intersection of one man\u2019s hobby with his professional background. <\/p>\n

Around 2005, rock art enthusiast Jon Harman saw NASA images depicting the Martian surface with and without the application of decorrelation stretch. Seeing how much detail the technique revealed, Harman, now retired in Pacifica, California, understood the implication for studying ancient, faded images. <\/p>\n

He also worked in medical imaging. \u201cI Googled it and found a NASA paper that explained how to do the algorithm,\u201d he said. \u201cI knew from my medical imaging experience that I could do it, so I did.\u201d <\/p>\n

The paper was written in 1996 by Ronald Alley, a JPL employee developing applications for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), a Japanese imaging instrument on NASA\u2019s Terra satellite. One of Alley\u2019s former supervisors at JPL had coinvented decorrelation stretch, and Alley had recognized its potential for gleaning information from ASTER imagery.  <\/p>\n

Harman made his plug-in for use with ImageJ, an open-source program developed by the National Institutes of Health.  <\/p>\n

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