NASA imaging method revives hidden ancient paintings at Angkor Wat and worldwide

Faded murals high in Angkor Wat’s central tower, depicting riders and a musical ensemble, were brought back into view using a NASA-originated image-processing technique known as decorrelation stretch. The algorithm, first described in a 1996 JPL paper by Ronald Alley for the ASTER instrument on NASA’s Terra satellite, was later adopted by rock-art enthusiast Jon Harman, who created an ImageJ plug-in and smartphone apps to apply the effect.

Harman’s work uncovered the Angkor paintings and about 200 similar artworks across the complex between 2010 and 2012. Dstretch has since been employed at archaeological locations under a Norwegian cliff, in an Egyptian tomb, a Canadian park, and a Mexican cave, as well as for studying Greek ruins and mummy tattoos. Harman reports handling roughly 200 requests for the tool each year, and scholarly papers continue to document its value for archaeology. The widespread adoption highlights how space-technology tools can transform heritage research.