fuzhenn/chinese_coordinate_conversion

An open-source javascript library for coordinate conversion between WGS84 and various encrypted chinese coordinate systems such as BAIDU, GCJ02.

Chinese Coordinate Transform

Coordinate or GeoJSON trasnforming from WGS84 to various encrypted Chinese coordinate systems such as BD09LL, GCJ02 and vice versa.

Supported coordinate reference systems (CRS)

• GCJ02 : Chinese encrypted coordinate system
• BD09LL : CRS used by http://map.baidu.com
• WGS84 : well-known CRS, aka EPSG:4326

Definition

convertor.transform(source, fromCRS, toCRS);

• source : a coordinate, array of coordinates, a GeoJSON or a array of GeoJSON to transform, possible values:
  • a coordinate: [x, y]
  • coordinate arrays: [[x1,y1], [x2, y2]] or more dimensions: [[[x1,y1], [x2, y2], [x3, y3]]]
  • a geoJSON object: { "type": "Point", "coordinates": [100.0, 0.0] }
  • a array of geoJSON objects: [{ "type": "Point", "coordinates": [100.0, 0.0] } , { "type": "Point", "coordinates": [101.0, 1.0] }]
• fromCRS : CRS transform from, possble values:
  • 'gcj02'
  • 'bd09ll'
  • 'wgs84' | 'EPSG:4326'
• toCRS : CRS transform to, same possible values with fromCRS

How to use

Node

    npm install chncrs

Browser

    <script src="chncrs.js"></script>
    <script type="text/javascript">
        var c = maptalks.CRSTransform.transform([114.68837663801743, 33.63312016454496], 'GCJ02', 'BD09LL');
    </script>

Example

    var convertor = require('chncrs');
    //convert coordinates from gcj02 to bd09ll
    var c = convertor.transform([114.68837663801743, 33.63312016454496], 'GCJ02', 'BD09LL');
    
    //convert a geoJSON object from gcj02 to bd09ll
    //can also be other geometry type, a Feature, even a FeatureCollection
    var geo = { "type": "Point", "coordinates": [100.0, 0.0] };
    var geo2 = convertor.transform(geo, 'GCJ02', 'BD09LL');

    
    //a geoJSON array
    var geos = [{ "type": "Point", "coordinates": [100.0, 0.0] } ,
                { "type": "Point", "coordinates": [101.0, 1.0] }];
    var geos2 = convertor.transform(geo, 'GCJ02', 'BD09LL');
    
    //a Feature
    var feature = { "type": "Feature",
              "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
              "properties": {"prop0": "value0"}
            };
    var feature2 = convertor.transform(geo, 'GCJ02', 'BD09LL');

    //a FeatureCollection
    var featureCollection = {
                "type": "FeatureCollection",
                "features": [
                    { "type": "Feature",
                      "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
                      "properties": {"prop0": "value0"}
                    },
                    { "type": "Feature",
                      "geometry": {
                          "type": "LineString",
                          "coordinates": [
                              [102.0, 0.0], [103.0, 1.0], [104.0, 0.0], [105.0, 1.0]
                          ]
                      }
                 ]
              };
    var featureCollection2 = convertor.transform(geo, 'GCJ02', 'BD09LL');