Developer tools

Map Coordinate Converter

Convert between WGS84, GCJ-02 (Mars coordinates) and BD-09, with the offset distance shown for each.

Runs locally in your browser

Input system Paste coordinates (order auto-detected)

Longitude Latitude

Try

WGS84

Raw GPS coordinates. Used by OpenStreetMap, GeoJSON and most non-Chinese services.

lng lat

GCJ-02

The mandated offset system for mainland China. Amap, Tencent and Google China use it.

lng lat

BD-09

Baidu’s own layer on top of GCJ-02. Only Baidu maps and APIs use it.

lng lat

WGS84 → GCJ-02 uses the published encryption formula and matches mainstream implementations exactly; the reverse has no closed form and is solved by iteration to under 1e-9 degrees (about 0.1 mm). Baidu’s formulas carry 0.00002 and 0.000003 correction terms, so BD-09 round trips are off by about 2 cm by construction. No offset is applied outside mainland China.