It's "impossible".

Private, independent geographical surveying is illegal in China. [0] So technically you can't do it even in the local coordinate system.

[0] https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat...

But I guess to OPs point, you could make a non-authoritative map based on satellite imagery, it just wouldn’t be legal to use in China.

OSM has an extensive article about mapping in China. Generally it's not allowed. Still, in the bigger OSM is quite accurate. :>

Anything that can be seen from a satellite is quite accurate, that's true, but oftentimes things like number of lanes, type or direction of the roads is unknown, footpaths in rural areas are very spotty. Basically anything that requires local human verification (addresses, business location, etc) is off limits and accuracy in those points comes from pre-ban times (or illegal activity).

At one point we spent some time reverse engineering the Chinese coordinate system, it’s actually quite fascinating. So terrible though.

But OSM actually doesn’t use that system! They use the normal coordinate system, which makes them unique across mapping services (and also a good tool to use to RE geojson away from chinas system).