China datums

Coordinate systems used in China

Web maps

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.

One finds one can replicate very closely the results of e.g., Sogou API (type=1) using the following parameters, here as we take a diagonal swath through the country:

$ perl -wle 'for($x=90, $y=20; $y<=50; $x++, $y++){print "$x $y"}'|
proj -E +proj=merc +k_0=1.000010881 +rf=294.9787 +a=6378137
...
116 46	12913201.44	5749320.52
117 47	13024522.14	5910526.61
118 48	13135842.84	6074798.25
119 49	13247163.55	6242305.46
120 50	13358484.25	6413230.50

Indeed, the only differences that remain appear to be the state mandated distortion... 似乎僅留政府所規定之偏移…

See also

• Taiwan datums