Quote Originally Posted by Quarktasche10 View Post
As i understand the shifting is not static. Is there an algorithm to get the correct values or is whole china virtually tiled and there is a database with different correction values for every tile?
That's right. The shift is location dependent. Let (x, y) and (x', y') be the original and shifted coordinates respectively, then

x' = f(x, y)
y' = g(x, y)

where f and g are two un-published functions strictly controlled by the Chinese government. The shifts x'-x and y'-y oscillate like a wave in each direction. Although there are many ways to find, fit or approximate f and g, no one wants to break the law by publishing a high precision version of f and g.