Definition
Baidu applies an additional polar offset on top of GCJ-02. Points taken from Baidu APIs are in BD-09; treating them as WGS84 or even as raw GCJ-02 without conversion will produce visible errors.
BD-09 vs GCJ-02 vs WGS84
Rough chain: WGS84 → GCJ-02 (national skew) → BD-09 (Baidu-specific). For GIS work you should label the datum in metadata and convert end-to-end with tested formulas or libraries.
When to use BD-09
Use BD-09 when ingesting or exporting data that must match Baidu tiles, geocoding results, or SDK samples. For cross-platform apps, standardize internally (often WGS84 or GCJ-02) and convert at the boundary.
FAQ
- Can I use BD-09 coordinates on a Gaode (GCJ-02) map?
- Not directly. Convert BD-09 to GCJ-02 (or both to WGS84) first so every layer shares one datum.
- Is BD-09 more accurate than WGS84?
- Accuracy is not “better”—it is a different reference. Choose the system that matches your data source and basemap.
- How do I batch-convert BD-09?
- Use the coordinate converter: set source to BD-09 and target to WGS84, GCJ-02, or an EPSG code as needed, then export the result.
- Where can I read about GCJ-02?
- See the GCJ-02 guide in the help section for the China encrypted coordinate context that BD-09 builds upon.