Foreigners using GPS devices on the mainland risk being detained by police or national security agents if they suspect them of conducting illegal mapping. 'It's better for [your] safety not to turn on the GPS function [on your cellphone],' a State Bureau of Surveying and Mapping official said. The bureau announced 10 days ago that it was launching a year-long crackdown this month on illegal surveying, with foreigners among its prime targets. Six ministries are involved in the campaign. Its announcement cites the detention in December 2007 of a foreigner in a village near Luoyang in Henan province. State security agents found a number of locations marked on his hand-held Global Positioning System device and used that as evidence for his arrest, the bureau said, without elaborating. The South China Morning Post spoke to a bureau official, who identified the detainee as American mining expert Calvin Herron. According to his online profile, Mr Herron is 'an exploration geologist with more than 20 years experience in acquisition and management of precious and base metals projects in the western United States' and experience 'managing gold and lead-zinc exploration programmes' on the mainland. The official said Mr Herron was deported four months later after the authorities confiscated his equipment and data and fined him 100,000 yuan (HK$113,700). Mr Herron could not be reached for comment. Xu Shijie, a guided-missile expert at Beihang University, said there were missile facilities near Luoyang and Mr Herron had probably been arrested because he was getting too close to them. He is not the only foreigner to have been detained for surveying and mapping on the mainland without approval. At least six Japanese visitors were reportedly arrested in the Xinjiang Uygur autonomous region between 2005 and 2007. Bureau deputy director Song Chaozhi told China News Service earlier that the bureau would intensify its watch on non-Chinese people using GPS devices for mapping and surveying purposes. '[Such behaviour] severely threatens China's national security,' Mr Song was quoted as saying. An anonymous article, possibly inspired by the crackdown and entitled 'How to Catch a Foreign Spy Mapping Chinese Terrain', is circulating in mainland internet chat rooms, urging people to watch out for foreigners using GPS devices. Beijing bans foreigners from conducting a wide range of topographical activities, from plotting terrain to aerial photography. Non-Chinese institutions or individuals intending to use mapping devices on the mainland must file a request to the central government - which can take months to approve; they must also be 'assisted' by mainland bodies and submit their data for vetting.