From 1960's to 1970's, the Chinese Army built some fortified artificial hills. Some of them are located in the Inner Mongolia, Western China. These large fortresses are surrounded by moats. For some of them it is still possible to see earthworks, trenches and ditches, the planning of which could have a symbolic meaning. We can argue this result form their digital outlining, obtained after an image processing of satellite images, based on edge detection.
['Amelia Carolina Sparavigna']
The fortresses of Ejin: an example of outlining a site from satellite images