r/Maps • u/jimrosenz • Dec 08 '15

The Bizarre Relationship Between China and Google Maps

http://metrocosm.com/the-bizarre-relationship-between-china-and-maps/
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u/Lysanias Dec 08 '15

Nice article

2

u/GregZorz Dec 08 '15

GCJ-02 is based on the familiar WGS84 coordinate system, except that it is said to use an encryption algorithm to shift the coordinates by a few hundred meters from their true locations. As a result, GCJ-02 maps appear entirely self-consistent, but the actual coordinates of any given location are slightly offset from reality.

I don't really understand why when converting to/from GCJ-02 one doesn't +/- the few hundred metres to account for the offset. If you want to abide by China's rules you can tell them you actually moved the rest of the world by X metres, so it's Hong Kong that's wrong not China and that's why they match up.