Two coordinate representations
WGS 84 is a global geodetic reference system widely used for GPS positions and GeoJSON exchange. GCJ-02 is an obfuscated coordinate system used in many digital map services in mainland China. Plotting WGS 84 coordinates directly over a GCJ-02-based basemap can produce an apparent misalignment.
What does ChinaBoundary do?
The interactive map uses AutoNavi for the basemap, and the page includes the coordtransform library for marker placement. The boundary-layer rendering logic is maintained separately. For GIS analysis, always inspect the raw download rather than assuming the visualization reflects a transformed downloadable dataset.
A useful validation workflow
- Identify the source CRS of the dataset from its metadata.
- Identify the basemap’s expected coordinate system.
- Compare several recognizable control points, not just one.
- If conversion is necessary, use a documented workflow and retain the original geometry.
GCJ-02 conversion is not equivalent to changing a CRS label. Do not relabel coordinates without transforming and verifying them.