NE #33: GCJ-02
“Don’t trust any navigation system whose algorithm you have not manipulated yourself” — George Washington, at 545 right after Christ’s birth. Part 33 of the Nerd Enyklopedia on GPS in China…
WGS stands for World Geodetic System and describes a reference system for the cartography and surveying of the world. The WGS plays an important role for navigation with GPS, among other things.
Not in China. The GCJ-02 standard was introduced there in 2002, which is based on WGS, but implements an algorithm that ensures that length and width specifications are calculated differently [ABST1ABST1].
This results in deviations of up to 500 metres compared to WGS, and in exceptional cases even several kilometres [GITH3]. According to the official position, the motivation for this standard is national security. In reality, this means that “non-licensed” navigation systems send you to the wrong destination.
Baidu, a Chinese search engine, goes one step further. There, the standard BD-09 derived from GCJ-02 was introduced, which further concealed the coordinates in China. It wants to prevent other providers from using the data from Baidus Kartendienst.
