Japan GNSS · 4 of 6 · counts dated

Reference stations in Japan: the state network, and the free one

Japan has two reference-station worlds that newcomers mix up. One is GEONET, about 1,300 government stations that define the national datum and feed the commercial correction services. The other is the community: a few hundred bases run by universities, companies and individuals who publish their streams for free. You will use the first indirectly and the second directly. Here is how each reaches your receiver.

GEONET: what it is

GEONET (GNSS Earth Observation Network System) is the continuously operating network of electronic reference points (電子基準点) run by the Geospatial Information Authority of Japan (GSI). As of April 2026 about 1,300 of them are in operation. They are the positional standard of the country: the national datum is realised through them, crustal deformation is monitored with them, and the centimetre services (CLAS, commercial network RTK) are computed from their data. Most stations are connected to GSI's central station continuously, with one-second data collected in near real time; remote islands and mountain sites are the exceptions.

Getting GEONET observations after the fact

Archived observations are available to registered users through GSI's data service at terras.gsi.go.jp, including SFTP access and RINEX in several versions (RINEX 4.01 was in trial release from September 2024). GSI also publishes the tools you will want next to the data: RINGO for RINEX preprocessing and RNXCMP for Hatanaka compression. If you post-process a survey in Japan, this is your reference data; a researcher's registration is the normal route.

Getting GEONET in real time: you do not, directly

This is the part that surprises engineers from countries where the state CORS network is open on an NTRIP caster. In Japan, GSI provides real-time GEONET data to private positioning-service providers through a distribution agency, the Japan Association of Surveyors, which also performs quality inspection. Those providers (Jenoba and Nippon GPS Data Service are two of the long-standing ones; survey-equipment makers run their own) sell network RTK, usually VRS, as a subscription. An individual does not connect to a GEONET station's raw stream.

So for real-time centimetres in Japan your honest options are: a commercial network-RTK subscription; CLAS from the satellite (see the CLAS page); or a free community base station within a short baseline. Many professionals carry all three.

The free community: the goodwill stations

Japan has a tradition of goodwill base stations (善意の基準局): a university lab, a prefectural research centre or a farm puts up a receiver and publishes the RTCM stream on a public NTRIP caster for anyone to use. There is a long-running notice board for them, and the streams sit on casters such as RTK2GO, BizStation (ntrip1.bizstation.jp), GeoRTK and Centipede-RTK. These stations are not the national datum; their coordinates are as good as the operator set them, and a wrong base height will follow you into your data (this site has a measured example, 122 m off). Used with that in mind, they are excellent.

KUON GEO polls the public casters every ten minutes and publishes the list of Japan's stations with position, format, RTCM message types, constellations, whether authentication is required and whether the station answered recently. On 13 August 2026 the count was 417 stations in Japan and 2,485 worldwide. The list is free and needs no key; the reasoning is written in letting the receiver pick the base. Paid or authenticated stations are flagged, not hidden, so your client can skip them.

A base within about 10 km gives you the best chance of a quick Fix; beyond 40 km a Fix becomes unreliable. KUON MAP has a baseline checker that measures the distance from any point to the nearest online base, and the ranking shows measured uptime so you can choose a station that is actually there at 6 a.m.

Putting it together

Sources

GSI, What GEONET is and Use of electronic reference point real-time data; terras.gsi.go.jp (data service). Japan Association of Surveyors, real-time data distribution service (about 1,300 stations as of April 2026, distribution agency role). Goodwill base-station board, rtk.silentsystem.jp. Station counts: KUON GEO's own 10-minute polling, 13 August 2026.