Japanese Coordinate Systems: JGD2011 and Seismic Adjustments
Japan's geodetic history is highly complex due to its position on multiple active tectonic plates. The legacy Tokyo Datum (based on the Bessel 1841 ellipsoid) differs from modern global frameworks by over 400 meters. The devastating 2011 Tohoku earthquake triggered massive crustal deformation, forcing the Geospatial Information Authority (GSI) to update the Japanese Geodetic Datum 2000 (JGD2000) to the current JGD2011 standard.
⚡ Local EPSG vs WGS84 Compare
Compliance Check🔑 Japan Geodetic Summary
- Governing Agency: Geospatial Information Authority of Japan (GSI)
- Official Datums: Tokyo Datum, JGD2000, JGD2011
- Key EPSG Codes: EPSG:4301 (Tokyo), EPSG:6668 (JGD2011)
- Typical Error Magnitude: 400+ meters (Tokyo Datum to JGD2011)
Legal Compliance & Professional Risks
Under the Japanese Survey Act, JGD2011 is the legally mandated datum for all public surveys. Transforming historical property records (often still referenced to the old Tokyo Datum) or pre-2011 data into JGD2011 requires the use of official GSI parameter files and software grids to maintain legal standing.
⚠️ Common Financial Failure Scenario
In real estate development, relying on a 1980s cadastral map (Tokyo Datum) and attempting to overlay it on modern JGD2011 satellite imagery involves a 400+ meter discrepancy. Even more subtle are the shifts caused by the Tohoku earthquake (up to several meters depending on proximity to the epicenter). Using JGD2000 coordinates for new construction today without applying the 2011 crustal deformation grids results in boundary violations.
Technical Architecture
The Tokyo to JGD2011 Transformation Pipeline
The transition from Tokyo Datum to JGD2011 is not a simple translation. EPSG operation 6714 defines an official PROJ pipeline using GSI grid files.
It utilizes a multi-step horizontal grid shift method (`+proj=hgridshift`) leveraging the `tky2jgd.gsb` grid for the primary datum shift, followed immediately by the `touhokutaiheiyouoki2011.gsb` grid to account for the massive tectonic displacement of the 2011 earthquake.
Failure to apply both grids sequentially means the spatial data ignores one of the largest modern crustal deformations ever recorded.
🛡️ Official Transformation Method Configuration
For integration into PROJ, QGIS, Civil3D, or customized GNSS controllers, the following parameters are the definitive standards verified by Geospatial Information Authority of Japan (GSI):