,
Indonesia (2025) The primary purpose of QZSS is to increase the availability of GPS in Japan's numerous
urban canyons, where only satellites at very high elevation can be seen. A secondary function is performance enhancement, increasing the accuracy and reliability of GPS-derived navigation solutions. The Quasi-Zenith Satellites transmit signals compatible with the GPS L1C/A signal, as well as the modernized GPS L1C, L2C signal and L5 signals. This minimizes changes to existing GPS receivers. Compared to standalone GPS, the combined system GPS plus QZSS delivers improved positioning performance via ranging correction data provided through the transmission of submeter-class performance enhancement signals L1S, L6D, and L6E from QZSS. It 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.
Signals and services The QZSS provides the following classes of public service: • The PNT (positioning, navigation, and timing) service complements the signals used by the GPS, essentially acting as extra satellites. The QZSS satellites sync their clocks with GPS satellites. The service broadcasts at frequency bands L1C/A, L1C, L2C, and L5, the same as GPS, with largely interoperable formats. The L1C and L2C messages include time differences from GPS, GLONASS, and Beidou to allow simultaneous use of multiple satnav systems. • Two ionospheric parameter sets are provided, one for a rectangular area enclosing Japan, the other for a larger area. • The SLAS (sub-meter level augmentation service) provides a form of
GNSS augmentation for GPS interoperable with other GPS-SBAS system. It transmits on L1 and is called L1S. It contains
differential GPS data in the form of pseudorange errors at monitoring stations. It augments multiple constellations. • The
Michibiki Satellite-based Augmentation Service (MSAS), transmitting on L1 as L1Sb. EGNOS-like state-space data structure. • The CLAS (centimeter level augmentation service) provides high-precision positioning compatible with the high-accuracy service (HAS, E6) of
Galileo. • The MADOCA-PPP (Multi-GNSS Advanced Orbit and Clock Augmentation –
Precise Point Positioning) service is an augmentation service independent from CLAS. It also broadcasts on L6 but uses a different modulation known as L6E. It augments multiple constellations. It transmits data about GNSS orbit/clock correction, satellite code/phase bias, and GNSS accuracy. • An ongoing experiment transmits wide-area ionospheric correction data on L6D in place of CLAS on select satellites. The ionospheric correction data is defined for specific rectangular or circular regions in Asia and Oceania, with their definitions also broadcast by the satellites. • The DC Report (Satellite Report for Disaster and Crisis Management) service broadcasts on L1S and provides information on natural disasters such as floods and earthquakes and other safety-critical information such as missile launches. It is incorporated into SLAS data. • The QZSS Signal Authentication Services (SAS), which provides
cryotpgraphic signatures to prevent (or rather, detect) GNSS spoofing and other signal spoofing. • Navigation Message Authentication (NMA) which specifically protects PNT signals. • QZSS NMA, which transmits the signature along with the PNT signals on their respective bands and modulations. • GPS and Galileo NMA, which transmits the signatures on the L6E signal in a time-divided manner with MADOCA-PPP. The other classes of service are not publicly available: • The PTV (Positioning Technology Verification) service broadcasts on L5S. The documentation only describes a "null" message type. • The Q-ANPI (QZSS Safety Confirmation Service) is an authorized short message service. It is not seen on the website as of 2026. Unless otherwise stated, "multiple constellations" refers to GPS, GLONASS, Galileo, QZSS, and BeiDou.
Coverage QZSS coverage can be divided into two topics: the visibility of the satellite and the applicability of the augmentation data. Every user with a view of the satellite can make use of PNT navigation messages, the location-independent elements of augmentation messages (satellite orbit and clock corrections), and the message authentication service. Only users near or in the intended areas can make effective use of the location-dependent elements of augmentation messages (ionospheric correction, local accuracy estimate) and other services such as natural disaster alerts. File:QZSS-Visible-area-elv-angle ps-qzss-003.png|Ground visibility and elevation of QZS-3 File:QZSS-Visible-10deg-area ps-qzss-004.png|Areas with uninterrupted visibility of at least one QZO satellite (QZS-1R/2/4) at an elevation of at least 10°, assuming the full 7-satellite constellation File:QZSS-Typical-Ground-Track_ps-qzss-004.png|Typical ground track of planned 7-satellite constellation • The ionospheric parameters from PNT is defined for a "Japan area" (50°N–22°N, 110°E–160°E) and a "broad area" (60°N–60°S, 60°E–160°W) respectively. • The SLAS service area can be found in the article
Michibiki Satellite-based Augmentation Service (MSAS). As of October 2025 it achieves LPV200 over the home islands, the Korean peninsula, the Ryukyu island chain, and
Bonin Islands. It achieves LPV250 over Taiwan on days of normal ionospheric activity, but is unable to during intense ionospheric activity. The FY 2025 assessment report uses the 13 MSAS base stations for testing and produces essentially the same coverage. • The CLAS service has essentially the service area as SLAS. The ionospheric and tropospheric corrections are transmitted as gridded data covering these areas. • The FY2025 MADOCA-PPP performance report shows a large intended service area ranging from 60°N–60°S, 60°E–160°W. With that said, it broadcasts no location-dependent information. • MADOCA-PPP experimental ionospheric correction covers Japanese home islands, Ryukyu island chain, Bonin Islands, the Philippines, Australia, and a small area around Jakarta. • The DC Report (DCR) service is managed by the
Japan Meteorological Agency which publishes reports about events affecting Japan. The DCR also includes tsunamis and earthquakes affecting the northwest Pacific Ocean. The Extended DC Report (DCX) service is intended to also be used by international diaster prevention organizations. == Public outreach ==