4 ms·
The offsets are not random, but algorithmic, using the GCJ-02 datum. Of course, legal access to use the GCJ-02 algorithms requires that you kowtow to the Chine
by jpatokal 11y ago
The offsets are not random, but algorithmic, using the GCJ-02 datum. Of course, legal access to use the GCJ-02 algorithms requires that you kowtow to the Chinese government:
https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat...
- csours 11y ago> It uses an encryption algorithm[13] which adds apparently random offsets to both the latitude and longitude, with the alleged goal of improving national security. You're both right! It uses reversible randomness apparently. Wonder how hard the algorithm and seed(s) are to figure out
- poizan42 11y ago> reversible randomness Yeah, we have a word for that: encryption
- kristofferR 11y agohttps://wuyongzheng.wordpress.com/2010/01/22/china-map-deviation-as-a-regression-problem/ https://wuyongzheng.wordpress.com/2010/01/22/china-map-devia... There are now many OSS-tools that convert between the global coordinate system standard (WGS-84) and the Chinese deliberately incompatible coordinate systems (GCJ-02 and BD-09).