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.
Senior Researcher Tetsuo Tamama at Japan's Defense Research Center says the worries about the U.S. system may be exaggerated.
"Most of the public is wrong," he said. "The U.S. government and military will never come to charge for the GPS service and they will never come to turn it off."
U.S. officials have repeatedly said the system will remain available, but those assurances have not erased anxieties.
Britain, France, Germany and Italy are planning to build a new navigation system, called Galileo, and may team up with China to do it.
In Japan, officials are looking to build a system known as "quasi-zenith" that would augment, rather than replicate, the GPS system. By putting up just a few satellites - with one always at a high-elevation angle over Japan - the country would enjoy enhanced coverage and accuracy. Proponents say it would be so accurate it could even track lane changes made by cars.
Aerospace consultant Lance Gatling in Tokyo says that while Japan's government does not mind using the American GPS system, it does not want to be wholly reliant on it.
"Some of the impetus behind having this quasi-zenith satellite system is the possibility of having a limited independent capability in the absence of the GPS signal," said Lance Gatling.
The Advanced Space Business Corporation, the consortium that wants to build the Japanese system, is eager to get its satellites aloft before the European system begins working.
"So that is the reason why we plan to go to satellites in 2008," said Kiyoshi Toriyama, the executive vice president of Advanced Space Business Corporation. "That is because of Galileo is going to start service around that time so we don't want to be delayed."
The consortium, which includes giant corporations such as Mitsubishi, Hitachi and Toyota, wants the government to pay half the two-billion dollar cost of the project.
Consultant Lance Gatling says the project could not come at a better time for Japan's space industry and its consumer electronics makers.
"It may well be that this helps spur a new growth in the GPS equipment market," he said. "And it's a significant market for Japanese electronics manufacturers. And if it works here, it may well work other places."
The consortium now is trying to convince the government of the new system's advantages. Mr. Toriyama says it will include new communications and broadcasting services, such as helping locate stolen cars, or giving train passengers access to the Internet.
"It will include saving lives or emergency communications," said Kiyoshi Toriyama. "We calculated billions of dollars of social benefit."
One roadblock is that government purse strings have been drawing tighter, as Tokyo struggles with a record budget deficit and a long economic slump.
Proponents are hoping to convince politicians that the quasi-zenith system is an essential part of Japan's future. And, as the Japanese unemployment rate lingers at record highs, they hope politicians also might be swayed by the promise of 11,000 new jobs related to the system.