Map applications have become an indispensable ally for many: we use them to get to our destinations on foot, by public transport or by car and they are very useful to get an idea of what a city is like. we don’t know yet. as.
If you’ve ever used tools like Google Maps, you’ll be used to satellite view, a very useful option for viewing a particular area with a much higher level of detail. Of course, this won’t be very useful if you want to look at a map of China.
No matter which region of China you look at: all the maps are wrong
Simply use a platform like Google Maps and zoom in on any region in China. Although in the default view everything seems to be in order, if you switch to the satellite view you will see that everything seems to be moving: The roads are not where they should be and you can even see streets in the water.
As you can see in the image above, the satellite view never coincides with the geographic features of the map displayed on the screen. In some cases it’s not very noticeable, but if you look at an area where there’s a river or relevant point of interest, you’ll see it’s quite pronounced. But what is the reason?
This is a widely documented problem and known colloquially as GPS lag problem. In fact, we see that it even has an entry on Wikipedia. In Service Objects they explain in detail what this problem is, which arises from the fact that China does not use the same GPS standard as the rest of the world when plotting coordinates on a map.
This seems like a mistake, but it’s intentional and there’s a compelling reason.
The reason behind this move on maps of any region of China is that the country requires all maps to use a coordinate system known as GCJ-02. This system presents a small variation compared to the WGS-84 system, which is the one used practically throughout the world.
As we mentioned, you can easily check what we are talking about if you look at the map of any region in China. If you look closely, you’ll see that sometimes the difference between the default map and the satellite view doesn’t seem very big. The reason is that the variation is not always the same
It all starts with a law known as Surveying and Mapping Law entered into force at the end of 2002. This law is responsible for controlling which companies can exercise activities related to surveying and mapping within the borders of China. There are currently just over a dozen companies authorized to carry out this type of activity (and they are all of Chinese origin).
This means that foreign companies must work with a company that has a permit. In the case of Google, the company is known to have worked with a company known as Automatic navigation to obtain data from the GCJ-02 system and be able to use it in Google Maps.
As we read in a detailed article published on Medium by Anastasia Bizyayeva, all of the above means that companies like Google can take two different paths:
- Choose to use data from the GCJ-02 system both in the satellite view and in the default map. This will match the two views, but will cause errors at the country’s border: China will not appear properly connected to the rest of the world.
- The other option is to use a different system for each card., which makes the country appear correctly compared to the rest of the countries on the map. The problem, as we’ve already seen, is that the satellite view doesn’t match the default map.
Originally, the website google.cn/maps (which is no longer available due to censorship of Google services in China) used the GCJ-02 system in both the default view and the satellite view, so the country information displayed on the screen were correct in both cases. Currently, in the rest of the world (google.com/maps) the GCJ-02 system is used for the default map and WGS-84 for the satellite view, which causes the problem we talked about.
By | Service objects and Anastasia Bizyayeva (Average)
Cover image | Own production
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