Japan plans own GPS satellites

The first of three Quasi-Zenith satellites will be launched in 2009

Japan plans to launch a fleet of satellites which will improve the accuracy of the US Global Positioning System (GPS) in East Asia and Australia.

The first of three Quasi-Zenith satellites will be launched in 2009, if the project wins approval, according to local media reports. 

Signals from the satellites will be combined with signals from the existing US-owned GPS satellites, greatly improving the accuracy of GPS navigation in Japan and countries to its south.

Media reports suggest that the new system could reduce the margin of error in GPS locations to about 20cm in Japan.

Existing GPS accuracy is degraded in Japan because the GPS satellites orbit over the equator, and their signals are easily blocked by mountainous terrain and the 'urban canyon' effect in crowded cities. 

Special GPS receivers will be required to take advantage of the new satellites. It is unclear how much these will improve GPS accuracy outside their intended coverage zone when one of the Japanese satellites is in range.

The Japanese government initially looked to private industry to cooperate with funding for the project, but local companies dropped out of the talks.

They complained of a lack of high-level commitment and were uncertain whether they could generate a profit, according to unnamed sources cited by the Yomiuri Shimbun .