GIS開發(fā)：geojson圖層批量坐標(biāo)轉(zhuǎn)換
在沒有規(guī)律的坐標(biāo)偏移情況下，如國(guó)內(nèi)在線地圖偏移和經(jīng)緯度轉(zhuǎn)換，可以進(jìn)行方便進(jìn)行單個(gè)坐標(biāo)的轉(zhuǎn)換，轉(zhuǎn)換圖層就需要自己進(jìn)行開發(fā)了。
感謝coordtransform庫(kù)的作者，這里使用了coordtransform進(jìn)行偏移坐標(biāo)的轉(zhuǎn)換。
//引入fs和coordtransform庫(kù)
const?fs?=?require('fs');
const?coordtransform?=?require('coordtransform');
//geojson矢量對(duì)象處理
function?dataByfeaturetype(_feature)?{
????this.datafeature?=?_feature;
????this.featuretype?=?_feature.geometry.type;
????this.coords?=?_feature.geometry.coordinates;
????this.newcoords?=?[];
}
//點(diǎn)、線、面中數(shù)據(jù)坐標(biāo)遍歷處理
dataByfeaturetype.prototype.handlePoint?=?function?()?{
????this.newcoords?=?coordtransform.wgs84togcj02(this.coords[0],?this.coords[1]);
}
dataByfeaturetype.prototype.handleMultipointOrLinestring?=?function?()?{
????let?_tempCoords?=?[];
????for?(let?_udx?=?0;?_udx?<?this.coords.length;?_udx++)?{
? ?//這個(gè)根據(jù)自己的需要，選擇坐標(biāo)的偏移處理函數(shù)
????????_tempCoords.push(coordtransform.wgs84togcj02(this.coords[_udx][0],?this.coords[_udx][1]));
????}
????this.newcoords?=?_tempCoords;
}
dataByfeaturetype.prototype.handleMultiLineStringOrPolygon?=?function?()?{
????let?_tempCoords?=?[];
????for?(let?_udx?=?0;?_udx?<?this.coords.length;?_udx++)?{
????????let?_evCoords?=?[];
????????for?(let?_ndx?=?0;?_ndx?<?this.coords[_udx].length;?_ndx++)?{
//這個(gè)根據(jù)自己的需要，選擇坐標(biāo)的偏移處理函數(shù)
????????????_evCoords.push(coordtransform.wgs84togcj02(this.coords[_udx][_ndx][0],?this.coords[_udx][_ndx][1]));
????????}
????????_tempCoords.push(_evCoords);
????}
????this.newcoords?=?_tempCoords;
}
dataByfeaturetype.prototype.handleMultiPolygon?=?function?()?{
????let?_tempCoords?=?[];
????for?(let?_udx?=?0;?_udx?<?this.coords.length;?_udx++)?{
????????let?_polygons?=?[];
????????for?(let?_ndx?=?0;?_ndx?<?this.coords[_udx].length;?_ndx++)?{
????????????let?_polygon?=?[];
????????????for?(let?_tdx?=?0;?_tdx?<?this.coords[_udx][_ndx].length;?_tdx++)?{
????????????????_polygon.push(coordtransform.wgs84togcj02(this.coords[_udx][_ndx][_tdx][0],?this.coords[_udx][_ndx][_tdx][1]));
????????????}
????????????_polygons.push(_polygon);
????????}
????????_tempCoords.push(_polygons);
????}
????this.newcoords?=?_tempCoords;
}
//根據(jù)圖層的不同類型，選擇處理方法
dataByfeaturetype.prototype.handleByType?=?function?()?{
????switch?(this.featuretype)?{
????????case?"Point":
????????????this.handlePoint();
????????????break;
????????case?"MultiPoint":
????????case?"LineString":
????????????this.handleMultipointOrLinestring();
????????????break;
????????case?"MultiLineString":
????????case?"Polygon":
????????????this.handleMultiLineStringOrPolygon();
????????????break;
????????case?"MultiPolygon":
????????????this.handleMultiPolygon();
????????????break;
????}
}
//獲取數(shù)據(jù)處理結(jié)果
dataByfeaturetype.prototype.getResult?=?function?()?{
????this.datafeature.geometry.coordinates?=?this.newcoords;
????return?this.datafeature;
};
//輸入文件
fs.readFile('輸入geojson文件',?{
????encoding:?'utf-8'
},?(err,?res)?=>?{
????if?(err)?return;
????let?_geojsondata?=?JSON.parse(res);
????let?_newfeatures?=?[];
????let?_features?=?_geojsondata.features;
????for?(let?_fdx?=?0;?_fdx?<?_features.length;?_fdx++)?{
????????let?_feature?=?_features[_fdx];
????????let?_featurehandle?=?new?dataByfeaturetype(_feature);
????????_featurehandle.handleByType();
????????_newfeatures.push(_featurehandle.getResult());
????}
????_geojsondata.features?=?_newfeatures;
??//輸出處理結(jié)果
????fs.writeFile("輸出geojson",?JSON.stringify(_geojsondata),?(err)?=>?{
????????console.log(err);
????});
});
