GCJ-02 to BD-09 Converter
About GCJ-02 Coordinate System
GCJ-02 (Mars Coordinate System) is a geodetic datum used in China for geospatial data. It applies an encrypted offset to WGS84 coordinates to comply with national regulations.
Developed by the Chinese National Bureau of Surveying and Mapping, GCJ-02 was introduced to implement the national security policy on geospatial information. Most Chinese map services use this system.
GCJ-02 is used by all Chinese government-approved map services including AMap (Gaode), Tencent Maps, and Apple Maps in China. It is required for any mapping application operating within mainland China.
GCJ-02 applies a non-linear offset algorithm to WGS84 coordinates, shifting positions by up to several hundred meters. The exact algorithm is classified by the Chinese government.
The encryption offset only applies within mainland China. Coordinates outside China pass through without modification.
GCJ-02 is the mandatory coordinate system for all commercial map services operating in China. Converting between WGS84 and GCJ-02 is essential for international data integration.
About BD-09 Coordinate System
BD-09 (Baidu Coordinate System) is a geodetic system developed by Baidu, based on GCJ-02 with additional encryption for use in Baidu Maps and related services.
Baidu developed BD-09 by applying a secondary encryption layer on top of GCJ-02 to further obfuscate coordinates. It is proprietary to Baidu and used exclusively in their mapping ecosystem.
BD-09 is used exclusively in Baidu Maps, Baidu Navigation, and Baidu LBS API. It is the most encrypted coordinate system among Chinese map services.
BD-09 adds a second encryption layer on top of GCJ-02, making it the most heavily obfuscated coordinate system used in China.
Used exclusively within Baidu's mapping platform. If you're developing with Baidu Maps API, all coordinates must be in BD-09 format.
Conversion between BD-09 and other systems relies on reverse-engineered algorithms that provide sub-meter accuracy.
GCJ-02 → BD-09 Conversion Guide
// GCJ-02 → BD-09
x = gcjLon
y = gcjLat
z = √(x² + y²) + 0.00002 × sin(y × 3000 × π / 180)
θ = atan2(y, x) + 0.000003 × cos(x × 3000 × π / 180)
bdLat = z × sin(θ) + 0.006
bdLon = z × cos(θ) + 0.0065GCJ-02 to BD-09 applies Baidu's proprietary secondary encryption. The transformation converts Cartesian coordinates to polar form, applies sinusoidal perturbations to the radius and angle, then converts back to Cartesian with an additive offset of 0.006° in latitude and 0.0065° in longitude.
- Input GCJ-02 coordinates from any Chinese map service (AMap, Tencent Maps, etc.)
- The tool applies the BD-09 encryption algorithm
- Output is compatible with Baidu Maps API
- Use the reverse conversion for integrating Baidu data with other systems
- BD-09 has the strongest encryption among Chinese coordinate systems
- The offset between GCJ-02 and BD-09 is typically 50-100 meters
- Baidu Maps is the only major service using BD-09