Originally Posted by
ORAC
ORAC these are ground-reliant systems.
The QZSS satellites do act like 'special' GPS satellites located optimally for Japan but the attached enhancement services (CLAS, SLAS) rely on many many ground stations uploading their known vs measured position errors to the system.
An 'error map' is then calculated and capable receivers can obtain it from the satellite and then determine the system error that applies in their locality. That provides the sub-meter and centimeter level accuracy. No nearby ground stations = no improved accuracy.