Difference Between Tokyo Datum and JGD2011

1. The Massive Local to Global Shift

Historical map data in Japan was defined using the Tokyo Datum (Bessel 1841 ellipsoid). When GPS was widely adopted, a massive discrepancy emerged: raw WGS84/ITRF coordinates varied from Tokyo Datum coordinates by over 400 meters depending on the region.

2. The Evolution: JGD2000 and JGD2011

To align with global satellite systems, Japan shifted entirely to the Japanese Geodetic Datum 2000 (JGD2000), which tied directly into the ITRF. However, following the catastrophic 2011 Tohoku earthquake, portions of eastern Japan shifted physically by several meters. The Geospatial Information Authority of Japan (GSI) released JGD2011 to account for this violent tectonic deformation.

3. Transformation via GSI Grids

Transforming coordinate data from Tokyo Datum to JGD2011 requires the use of regional grid parameter files provided by GSI.

• A straightforward 3-parameter or 7-parameter shift is mathematically insufficient given the heavy localization distortions present in the 19th-century Tokyo Datum network.