Difference between revisions of "China datums"

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m (add category)
(merely the Clarke 1866 ellipsoid!)
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==Datums in China==
 
==Datums in China==
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Please see e.g., http://www.asprs.org/a/resources/grids/05-2000-china.pdf .
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On this page we aim to just supplement the more widely known information.
  
 
==Coordinate systems used in China==
 
==Coordinate systems used in China==
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===Web maps===
 
===Web maps===
 
 
觀測中國電子地圖諸網站常見座標系統,
 
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.
 
An observation of Chinese web mapping sites shows various non longitude /  latitude systems in use.
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visible in the URLs generated when "sharing" map views with friends.
 
visible in the URLs generated when "sharing" map views with friends.
  
One finds one can replicate very closely the results of e.g.,
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Also a factor is the state mandated distortion... 另需考慮政府所規定之偏移…
[http://map.sogou.com/api/documentation/javascript/api2.0/interface_translate.html 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"}'|
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====搜狗 Sogou====
[http://proj.osgeo.org/ proj] -E +proj=merc +k_0=1.000010881 +rf=294.9787 +a=6378137
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*[http://map.sogou.com/api/documentation/javascript/api2.0/interface_translate.html Sogou API] (type=1)
...
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Experimentation proves they are merely using the
116 46 12913201.44 5749320.52
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[http://en.wikipedia.org/wiki/Alexander_Ross_Clarke Clarke] 1866 ellipsoid,
117 47 13024522.14 5910526.61
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a=6378206.4 rf=294.978698213898 .
118 48 13135842.84 6074798.25
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  $ [http://proj.osgeo.org/ proj] +proj=merc +ellps=clrk66
  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…
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====Google====
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*WGS84 longitude / latitude
  
 
==See also==
 
==See also==
 
*[[Taiwan datums]]
 
*[[Taiwan datums]]
  
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[[Category:Datums by country]]
 
[[Category:China]]
 
[[Category:China]]
[[Category:Datums by country]]
 

Revision as of 11:03, 1 March 2012

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.

Coordinate systems used in China

Paper maps

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.

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

搜狗 Sogou

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

$ proj +proj=merc +ellps=clrk66

Google

  • WGS84 longitude / latitude

See also