GPS and maps: offset coordinates in China

    Since I work in a map service, I recently discovered for myself that all coordinates in China are shifted by a secret algorithm. I have collected some interesting stories and information about this fact.

    There is only the border of China in this world

    How it works

    The Chinese government, led by the military, decided to protect itself by moving all the coordinates in the country. And all companies working with geo-data are required to follow these rules and shift coordinates received, for example, from GPS.

    As a result, all objects in China are not in their real place with an error of about 200m. With the exception of Hong Kong, which does not comply with this law.


    At the XDA forum , BoingBoing also wonders which firmware to use in China, so that the real location matches the distorted map. Chinese devices and firmware signed an agreement and received a secret algorithm, so everything will be fine with them.

    Since the map is distorted nonlinearly by several hundred meters, the real time of the walking route will deviate by 2-4 minutes. But near state borders and the border with Hong Kong, geographical points are gradually returning to normal.

    From the article " Why your GPS camera will not work in China ."

    Satellite imagery

    Few mapping services boast labels on satellite imagery in China, as their images are not distorted. But Baidu cards can - they deftly distorted the pictures, at the same time adding greenery and cheerfulness!

    Google vs Baidu satelite map tiles
    Comparison of satellite maps Google and Baidu (reference point - South Station in the lower left corner).
    Residents of China can not compare, so they do not have access to Google.

    The runner and his Nike + watch

    Mark van der Hayes bought a Nike + sports watch in California that records a jogging route and then displays it on a map. The watch worked great in the US and Europe, but something went wrong in China. Not only did he run along houses and rivers, 4 identical circles turned into a kind of loop!

    The result of distortion of GPS data for non-Chinese devices.


    The Chinese market is very interesting for many large companies, but in order to enter it you need to cope with such local features. And while remembering users from other countries who come to China to stay and do not want to get lost.

    PS For skeptics, there is a continuation in the form of the article " All Maps in China are Transformed " by Jian Shuo Wang and " China Map Deviation as a Regression Problem " by Wu Yongzheng.

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