A “QR code”? Maybe it’s an app. :-)
"A Google Maps satellite spotted a series of bizarre structures during a sweep of the Gobi desert in China - and the mysterious objects sparked a wave of speculation that they could be anything from 'codes' to be read from space to practice targets modelled on US cities. But it now seems likely that the structures are used to calibrate China's spy satellites, according to Natalie Wolchover of website Life's Little Mysteries."
And now we know.