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Coordinate System Converter

WGS84 · GCJ02 · BD09 — instant, private, 100% in your browser

Result

Latitude, Longitude (e.g. 39.9042, 116.4074)

Why Do Coordinate Systems Differ?

WGS84 — The Global Standard

Used by GPS satellites, Google Maps (outside China), and most international mapping APIs. Coordinates are geographically accurate worldwide.

GCJ02 — China's Encrypted Offset

Mandated by Chinese regulations, GCJ02 applies a non-linear cryptographic offset to WGS84 coordinates. Used by AutoNavi (Gaode), Tencent Maps, and Apple Maps in China.

BD09 — Baidu's Extra Layer

Baidu Maps adds an additional proprietary offset on top of GCJ02. Using WGS84 coordinates directly in Baidu APIs will result in visible map drift.

Privacy — Coordinates Never Leave Your Device

All conversions run entirely in your browser using open-source algorithms. No coordinates are sent to any server.

Frequently Asked Questions

What is the difference between WGS84 and GCJ02?

WGS84 is the global GPS standard. GCJ02 applies a government-mandated encryption offset required for maps published in China. The offset is typically 100–500 metres.

Can I convert BD09 back to WGS84?

Yes. The conversion is approximate but accurate to within 1–2 metres for coordinates inside mainland China.

Why does my pin appear in the wrong place on Baidu Maps?

You are likely using WGS84 coordinates in a context that expects BD09. Use this tool to convert before passing coordinates to the Baidu Maps API.

Is this tool accurate outside China?

Outside mainland China, GCJ02 = WGS84 (no offset is applied). BD09 is only used by Baidu and is relevant only in China.