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Monitoring of a cultural heritage site by Sentinel-2 images and change-detection analysis

The monitoring of archaeological sites declared World Heritage Sites is a fundamental activity to protect and safeguard cultural heritage. In this context, monitoring with sensors mounted on a satellite platform represents a valuable tool. The availability of satellite images at high temporal frequency allows a continuous monitoring of the areas to be protected. The images acquired with the Sentinel-2 constellation are available free of charge and with a high temporal frequency; this mean that it is possible a continuous monitoring of the areas to be protected. In addition, the change-detection techniques and, in particular, the "Image Differencing" technique may be used, thanks to its simplicity and speed of application, in the monitoring activity. This technique provides that to each radiance value of an image acquired on a given date, the corresponding values of another image dating back to a high date are subtracted; in other words, to each pixel of an image is subtracted the value of the corresponding pixel of a second image acquired on a different date from the first one. The investigation was conducted on the archaeological site of the Temple of "Ain Dara" located in Syria, which is recognized in 2011 as a UNESCO World Heritage Site. The temple was destroyed in January 2018.