GPS and Maps: Displaced Coordinates in China
Since I work in the map service, recently I made a discovery for myself that all coordinates in China are biased by a secret algorithm. I collected some interesting stories and information about this fact.
There is only the border of China in this world heremaps.cn
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The Chinese government, led by the military, decided to protect itself by shifting all coordinates in the country. And all companies working with geo-data are obliged to follow these rules and shift the coordinates obtained, for example, from GPS.
As a result, all objects in China are not in their real place with an error of about 200m. Except for the territory of Hong Kong, which does not follow this law.
On the XDA and BoingBoing forums, they also ask themselves 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 the state borders and the border with Hong Kong, geographical points smoothly return to normal.
From the article " Why your GPS-camera will not work in China ."
Few cartographic services can boast of labels on satellite images of China, since their images are not distorted. But Baidu cards can - they deftly distorted the pictures, at the same time adding greenery and cheerfulness!
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.
Mark van der Hayes bought a Nike + sports watch in California that records a jogging route and then displays on a map. The clock worked fine in the USA and Europe, but in China something went wrong. Not only did he run through houses and rivers, 4 identical circles turned into a kind of loop!
The result of the distortion of GPS data for non-Chinese devices.
The Chinese market is very interesting for many large companies, but in order to reach it you need to cope with such local features. And at the same time remember about the users from other countries who will 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.
There is only the border of China in this world heremaps.cn
')
How it works
The Chinese government, led by the military, decided to protect itself by shifting all coordinates in the country. And all companies working with geo-data are obliged to follow these rules and shift the coordinates obtained, for example, from GPS.
As a result, all objects in China are not in their real place with an error of about 200m. Except for the territory of Hong Kong, which does not follow this law.
Navigators
On the XDA and BoingBoing forums, they also ask themselves 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 the state borders and the border with Hong Kong, geographical points smoothly return to normal.
From the article " Why your GPS-camera will not work in China ."
Satellite imagery
Few cartographic services can boast of labels on satellite images of China, since their images are not distorted. But Baidu cards can - they deftly distorted the pictures, at the same time adding greenery and cheerfulness!
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.
Runner and his Nike + watch
Mark van der Hayes bought a Nike + sports watch in California that records a jogging route and then displays on a map. The clock worked fine in the USA and Europe, but in China something went wrong. Not only did he run through houses and rivers, 4 identical circles turned into a kind of loop!
The result of the distortion of GPS data for non-Chinese devices.
Conclusion
The Chinese market is very interesting for many large companies, but in order to reach it you need to cope with such local features. And at the same time remember about the users from other countries who will 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.
Source: https://habr.com/ru/post/162613/
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