hujiulong/gcoord
Gcoord
gcoord is a coordinate conversion library that transforms geographic coordinates between China's three major map coordinate systems: WGS-84, GCJ-02, and BD-09. It handles the offset corrections required by national encryption policies, converting GPS or API-derived coordinates to align with the projections used by Chinese map providers like Baidu, Gaode, and Google China.
The library provides direct conversions between all three systems, including WGS-84 to GCJ-02, WGS-84 to BD-09, GCJ-02 to BD-09, and their reverse transformations. It processes individual coordinate pairs, batches of coordinates, and entire GeoJSON objects, applying the same conversion to every point while preserving the original structure and properties.
Built as a standalone module with no external dependencies, gcoord uses double-precision arithmetic and precomputed offset tables to maintain sub-meter accuracy across transformations. The library is written in TypeScript and implements its conversion logic through static function dispatch, routing each request to the correct algorithm based on the source and target system identifiers.
Features
- Map Coordinate Converters - Converts geographic coordinates between WGS-84, GCJ-02, and BD-09 systems to correct offsets from national encryption policies.
- Geographic Coordinate Converters - Provides the core functionality of converting GPS coordinates between WGS-84, GCJ-02, and BD-09 map systems.
- Ellipsoid-Based Transformations - Provides the core ellipsoid-based coordinate transformation logic between China's three major map systems.
- Map Projection Offset Correctors - Adjusts GPS or API-derived coordinates to align with the specific projection used by Chinese map providers.
- BD-09 Coordinate Transformers - Converts coordinates to and from Baidu's BD-09 system for use with Baidu Maps.
- Coordinate Correctors - Adjusts GPS or API-derived coordinates to align with the specific projection used by Chinese map providers.
- BD-09 to GCJ-02 Converters - Converts geographic coordinates from the BD-09 system back to the GCJ-02 system.
- GCJ-02 to BD-09 Converters - Converts geographic coordinates from the GCJ-02 system to the BD-09 system used by Baidu Maps.
- Geographic Coordinate Conversion Libraries - Converts geographic coordinates between WGS-84, GCJ-02, and BD-09 map coordinate systems with a single function call.
- WGS-84 to BD-09 Converters - Converts geographic coordinates directly from the WGS-84 standard to the BD-09 system used by Baidu Maps.
- WGS-84 to GCJ-02 Converters - Converts geographic coordinates from the WGS-84 standard to the GCJ-02 system used by Chinese map services.
- Map Coordinate Offset Correctors - Adjusts coordinates from GPS or APIs to align with the projection used by specific Chinese map providers.
- GeoJSON Coordinate Converters - Applies coordinate system conversion to every point in a GeoJSON object while preserving its structure.
- Coordinate Transformers - Applies coordinate system conversion to every point in a GeoJSON object while preserving its structure.
- GeoJSON Traversers - Recursively traverses GeoJSON objects to apply coordinate conversion to every point while preserving structure.
- Batch - Converts an array of longitude-latitude pairs between map coordinate systems in a single operation.
- JavaScript Geospatial Libraries - Converts between common geographic coordinate systems.
