Japan mulls seven-satellite QZSS system as a GPS backup - See more at:

The Japanese government is considering adding an additional three satellites to the country’s domestic navigation system in order to ensure that it would work with or without the U.S.’s GPS system. Japan’s Quasi-Zenith Satellite System, or QZSS, currently calls for four satellites, of which only one is in orbit. Colonel Shinichiro Tsui, a counsellor in Japan’s Cabinet Office, said here that the next three QZSS satellites are all scheduled to launch this year, followed by service activation in 2018. Those satellites, provided by manufacturer Mitsubishi Electric, would augment GPS signals, Tsui said, honing their positioning accuracy from sub-meter to centimeters. More

(Source: SpaceNews - May 16)