Japan GNSS · 3 of 6 · for the engineer who will not stay in Japan
MADOCA-PPP: Japan's precise point positioning, broadcast across Asia-Oceania
CLAS stops at Japan's coast. MADOCA-PPP does not: it is the augmentation that QZSS broadcasts on L6E for the whole Asia-Oceania footprint, from Southeast Asia to Australia. If your receiver will travel, or your work is at sea, this is the one to know. It is Japan's quiet international instrument in positioning, and it is free.
What it is
MADOCA stands for Multi-GNSS Advanced Orbit and Clock Augmentation. JAXA's MADOCA software estimates precise orbits and clocks for GPS, GLONASS, Galileo, QZSS and BeiDou from a worldwide monitoring network; QZSS broadcasts those products as L6E messages, and a receiver that can demodulate L6 uses them for precise point positioning. Trial service started on 30 September 2022 and operational service on 1 April 2024. The corrections are orbit and clock (plus biases for ambiguity resolution), not the dense atmospheric grid that CLAS carries, which is why it can cover a continent and why it converges more slowly.
What to expect
| Property | Value |
|---|---|
| Coverage | Asia-Oceania, wherever L6E from QZSS is receivable |
| Convergence | About 20 to 30 minutes of continuous observation before the solution settles |
| Accuracy after convergence | Decimetre class; published evaluations show orbit products accurate to a few centimetres, good enough for ambiguity resolution |
| Cost | Free; no subscription, no key, no internet needed for the satellite path |
| Ionospheric correction | Wide-area ionospheric correction is to be added as a trial once QZS-6 and QZS-7 are in service, to shorten convergence |
The use cases the Cabinet Office names first are maritime and other long-duration, wide-area work. Read that as guidance: a fishing vessel, a survey ship, a tractor in Queensland or a long transect on foot benefit; a drone that lands every fifteen minutes does not have time to converge.
Three ways to get the stream
- From the satellite. An L6-capable receiver or a decoder such as the u-blox NEO-D9C outputs the L6E messages. This is the path that works at sea and in the field.
- Over the internet (organisations). The Cabinet Office distributes the same L6E and L6D messages by NTRIP for companies, research institutes and universities developing MADOCA-PPP receivers and applications. One account per institution, applied for through the Michibiki web inquiry form; accounts expire on 31 March and must be renewed each fiscal year. This is not a consumer service.
- For research, the raw observations. MIRAI, the GNSS Integrated Data Sharing System at go.gnss.go.jp, distributes real-time RTCM 3 and archived RINEX from more than 300 monitoring stations worldwide, free of charge with registration. It has run since 1 April 2022.
To experiment without hardware, the Cabinet Office publishes MADOCALIB, an open test library for MADOCA-PPP processing (version 1.4 was released in December 2024). If you come from an RTKLIB background it will feel familiar.
MADOCA-PPP next to CLAS and to Galileo HAS
| Service | From | Where | Class | Convergence |
|---|---|---|---|---|
| CLAS (L6D) | QZSS | Japan | Centimetre (PPP-RTK) | About a minute |
| MADOCA-PPP (L6E) | QZSS | Asia-Oceania | Decimetre (PPP) | 20 to 30 minutes |
| HAS (E6-B) | Galileo | Worldwide | Decimetre (PPP) | Minutes to tens of minutes |
They are not competitors so much as overlapping layers. A receiver that decodes L6 and E6 can hold all three and pick by location. What is particular to MADOCA-PPP is that the precise products are computed in Japan and broadcast from Japanese satellites across a region of several billion people; for an engineer based in Jakarta or Perth, that is a free correction source with no account, and it is the part of the Japanese system that travels.
Sources
Cabinet Office, MADOCA-PPP service overview (dates, coverage, convergence, ionospheric trial); Internet distribution of MADOCA-PPP (eligibility, account terms); MADOCALIB v1.4 release; MIRAI (free registration, RTCM 3 and RINEX). DATAGNSS, technical analysis (orbit accuracy figures).