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# A NASA Method for Processing Satellite Images Is Now Used to Read Faded Rock Art
- URL: https://theparnassian.com/en/metod-nasa-dlia-obrabotki-sputnikovykh-snimkov-primeniaiut-dlia-chteniia-vytsvetshikh-naskalnykh-izobrazhenii/
- Published: 2026-09-09T07:36:39.000Z
- Updated: 2026-10-01T05:25:14.000Z
- Author: Alexandr Radayev
- Tags: Archaeology, Heritage, Science

The technique is called decorrelation stretch. The algorithm was developed at NASA's Jet Propulsion Laboratory in Southern California, and its description was published in 1996 by a member of the laboratory's staff, Ronald Alley, in connection with an instrument that later flew on the Terra satellite.

The principle is as follows. Multispectral imaging records reflected light in several bands at once, and in neighbouring channels the brightness values are usually closely linked to one another, that is, they correlate. Decorrelation stretch severs this link and redistributes the colour differences across the whole available range, so that barely perceptible shades become sharply contrasting. In this way geologists obtain maps of the mineral composition of a surface, on which rocks indistinguishable to the naked eye can be seen.

The method came to archaeology by way of a private individual. Around 2005 Jon Harman, an amateur enthusiast of rock art from the city of Pacifica in California, saw Martian images processed in this way and supposed that the same device would bring out faded ancient paintings. Harman had experience of working with medical imagery and wrote an additional plug-in for the free scientific image-processing program ImageJ. The program was named DStretch.

The method was applied at Angkor Wat in Cambodia between 2010 and 2012, where some two hundred images were discovered, among them horsemen and musical ensembles. After that came the cave of San Borjitas in Baja California in Mexico, rock paintings in Norway, an Egyptian tomb, a park in Canada, ancient Greek buildings and tattoos on mummified bodies.

The author of the program says that he handles about two hundred requests a year, while the mobile applications he has released have been downloaded thousands of times. The effectiveness of the method has been confirmed by separate scholarly publications.

![](https://theparnassian.com/content/images/2026/09/photo_21387@09-09-2026_10-36-39.jpg)

![](https://theparnassian.com/content/images/2026/09/photo_21388@09-09-2026_10-36-39.jpg)