Around the world, governments, soldiers and civilians have come to rely on the Global Positioning System for all sorts of navigational uses

Around the world, governments, soldiers and civilians have come to rely on the Global Positioning System for all sorts of navigational uses. But the users rely on nearly 30 satellites operated by the U.S. Defense Department. As GPS becomes a part of everyday life, there is growing concern about this dependence on a U.S. government system. There is no place in the world where the Global Positioning System is so heavily used as Japan. Millions of drivers depend on dashboard GPS systems to guide them, and about four million cellular phones in Japan are equipped with GPS receivers. In much of the world, GPS satellite signals are used to track trucking and shipping fleets, airliners and trains. Worldwide sales of GPS equipment are estimated to be worth $16.5 billion this year, and the amount is expected to double by 2006. Japanese manufacturers enjoy a substantial share of that market. But many people around the world worry about relying on the GPS system, which the U.S. military owns. They fear the United States might begin to charge for using the system, or make the signal less accurate or cut it off entirely in time of war. That could cause huge problems for airline traffic and shipping. The only alternative now is a Russian military network, which also could be cut off.