Why points in China are shifted
Maps published in mainland China must use GCJ-02, an obfuscated version of WGS-84 that moves every point by a non-linear offset of roughly 100 to 700 metres. Baidu adds a second offset on top, called BD-09. If you place raw GPS coordinates on Amap or Baidu — or GCJ-02 coordinates on Google Earth or OpenStreetMap — they land on the wrong street.
| System | Used by |
|---|---|
| WGS-84 | GPS devices, OpenStreetMap, Google Earth, Mapbox, this site’s map |
| GCJ-02 | Amap (Gaode), Tencent Maps, Apple Maps and Google Maps inside China |
| BD-09 | Baidu Maps |
How to use the converter
- Choose which system your coordinates are in.
- Paste them (decimal, DMS or a map link) or click the map.
- Copy the version for the map you are using. The marker always shows the true WGS-84 position on this map.
Accuracy
WGS-84 → GCJ-02 uses the widely published transformation; the reverse direction is solved iteratively to better than a centimetre. BD-09 conversions follow Baidu’s published formula. Outside mainland China the offsets are zero and all three systems are identical.
Frequently asked questions
What is GCJ-02?
GCJ-02 is the coordinate system required for maps published in mainland China. It shifts WGS-84 GPS positions by a few hundred metres using a non-linear formula.
Which maps use BD-09?
Baidu Maps uses BD-09, which adds an extra offset to GCJ-02. Amap and Tencent Maps use GCJ-02.
Do I need this outside China?
No. Outside mainland China the three systems give the same coordinates.