Beijing is concerned that field data collected by foreigners could be used by hostile powers to help guided missiles hit key military and civilian installations, mainland experts say.
The development of intercontinental ballistic missiles has increased the demand for precise location data because a tiny error could send a long-range missile hundreds of kilometres off its target. In recent years, spy satellites have enabled countries to pinpoint a location from space.
But Xu Shijie, a guided missile expert at Beihang University, said satellite images alone were not enough for a precise hit. He said satellite photos were enough to guide a missile during the initial and middle phases of a flight, but more detailed input would be needed in the final leg to determine which building to hit.
'A satellite does not hover directly above a target to take a snapshot. When it looks at something on Earth, it is at an angle. Mapping onsite with a GPS (Global Positioning System) device could help calculate the angle very precisely, and the data could help a missile calibrate its approach to the target,' he said.
That concern was the main reason behind Beijing's recent crackdown on surveying and mapping in sensitive areas without permission. But the move was also helped by prevailing xenophobic sentiments on the mainland.
A popular article widely circulating in mainland internet chat rooms titled 'How to Catch a Foreign Spy Mapping Chinese Terrain' expresses such sentiments. The author, whose identity is unknown, urged mainlanders to watch out for foreigners using GPS and doing mapping-related activities.
'A foreigner walks down a highway and records the road on his GPS device. Whenever he comes across a key intersection, he will mark it down. When the war breaks out, packs of JDAM (Joint Direct Attack Munition) bombs will land on these targets precisely,' the article said.
