Introduction of Helmert orthometric heights in the vertical datum of Japan : another set of the Geodetic Coordinates 2000 of Japan

The vertical datum of Japan, which is realized with official heights at the benchmarks, had been updated for the first time in about 30 years and the new heights were put in force in April 2002. The heights were computed from the latest leveling data throughout Japan and detailed land gravity data were taken into account, for the first time in Japan, for yielding Helmert orthomeitric heights. On this occasion, the paper tries to give readers a brief description of the height systems, their relationship with gravity and the computation method employed, and the current, more precise vertical datum of Japan updated from the previously-employed normal orthometric heights.