QZSS enhances GPS services in the following ways: 1) Availability enhancement (improving the availability of GPS signals); and 2) Performance enhancement (increasing the accuracy and reliability of GPS signals).

QZSS enhances standalone GPS availability for any user that has visibility to, and can track, one or more QZSS satellites. This enhancement will be the greatest for users in the region of Japan because the constellation design is optimized for that area.
However, users in many other Asia-Pacific areas will also benefit from the enhanced geometric arrangement made possible by QZSS. This increases area and times at which positioning is possible in both urban and mountainous locations. The system also improves positioning accuracy by transmitting signals (L1C/A, L1C, L2C and L5) that are equivalent to modernized GPS signals.

Because the GPS availability enhancement signals transmitted from QZSS satellites are compatible with modernized GPS signals and interoperability is ensured, the system uses modernized GPS signals as a base, transmitting the L1C/A signal, L1C signal, L2C signal and L5 signal. This minimizes changes to specifications and receiver designs.

QZSS further improves standalone GPS accuracy by means of ranging correction data provided through transmission of submeter-class performance enhancement signals L1-SAIF and LEX. QZSS also improves reliability by means of failure monitoring and system health data notifications. QZSS also provides other support data to users to improve GPS satellite acquisition.