Why does my GPS coordinate show me in the middle of a river when I'm standing on a bridge? If you're developing map-based apps in China or other specific regions, you've likely encountered "Coordinate Drift."

1. WGS-84: The Global Standard

WGS-84 is the standard coordinate system used by the Global Positioning System (GPS). Most devices provide coordinates in this format. However, for legal and security reasons, some countries require data to be shifted before it can be displayed on a public map.

2. The China Problem: GCJ-02 and BD-09

In mainland China, all public maps must use the GCJ-02 coordinate system (often called "Mars Coordinates"). If you plot raw WGS-84 data on a GCJ-02 map, you'll see a drift of several hundred meters.

Furthermore, Baidu Maps uses its own system, BD-09, which adds another layer of complexity.

3. The Conversion Solution

To solve this, developers must use conversion algorithms. Our Coordinate Converter allows you to instantly switch between:

• WGS-84 to GCJ-02: For Google Maps (China) and AutoNavi (Gaode).
• GCJ-02 to BD-09: For Baidu Maps.
• BD-09 to GCJ-02: Converting back to the standard Mars coordinates.

Conclusion

Geospatial data is rarely "plug and play." By understanding the underlying coordinate systems and using the right conversion tools, you can ensure your users are always exactly where they should be on the map.