UK Daily Mail 
November 17, 2011
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.
She spoke to Jonathon Hill, a research technician at the Mars Space Flight Facility at Arizona State University, which operates many of the cameras used in Nasa’s Mars missions – who said the symbols are near-identical to US targets used to calibrate Corona spy satellites in the Sixties.
The existence of these calibration targets may seem suspicious, but Hill said it really isn’t; China was already known to operate spy satellites, along with many other countries, including the U.S.