Coal India's measures to prevent theft by electronically 'fencing' mining areas and fitting trucks with a GPS-based tracking system will be finished by the end of April, a government official said. As much as a fifth of the state-run company's annual output is stolen, costing it up to $1 bln yearly and feeding a huge black market. Coal India's modernisation plan includes tracking trucks and using Google maps to 'fence' mines, alerting managers if a truck diverts from its route. Coal Secretary Anil Swarup said reducing the coal stolen and improving the quality of coal sold were top priorities. Coal India, the world's largest miner, wants to nearly double output to a billion tonnes by 2020. It has already spent more than half its targeted budget of $45 million on an overhaul.