China datums

Datums in China

Please see e.g., http://www.asprs.org/a/resources/grids/05-2000-china.pdf . On this page we aim to just supplement the more widely known information.

觀測中國電子地圖諸網站常見座標系統， An observation of Chinese web mapping sites shows various non longitude / latitude systems in use.

Very many of them are plain Mercator projections. They are visible in the URLs generated when "sharing" map views with friends.

Also a factor is the state mandated distortion... 另需考慮政府所規定之偏移…

Experimentation proves they are merely using the Clarke 1866 ellipsoid, a=6378206.4 rf=294.978698213898 .

$ proj +proj=merc +ellps=clrk66