[kccqzy]

About this perturbation function: almost the entire world uses the WGS84 datum. The Chinese use a datum that's similar but subtly different. If you didn't account for this datum you got shifted roads and features. The technical information about this datum has never officially been made public, but only licensed to certain companies. I'm fairly certain Google doesn't have such a license. You can find reverse engineered info online but there's no guarantee that those are correct.

[oppositelock]

You're referring to GCJ-02. From best as I can figure, it adds some form multi-frequency noise to a shifted WGS84 coordinate, but it also seems that different companies are told to use different coefficients for the different noise frequencies, that's how they can tell if you're doing what you're told.

Regardless, it's difficult to work with. If you have a mapping license, you must also take serious precautions never to let the accurate map data leave China, or your Chinese employees are in deep trouble.