JS算法 GPS国际坐标转换成高德火星坐标

高德API坐标转换：http://lbs.amap.com/api/webservice/guide/api/convert/

算法优势

高德API自带坐标转换方法，每次转换都需要一次请求，效率太低。当你需要批量将GPS国际坐标转换成高德的火星坐标时，使用本算法，会有意想不到的性能提升。

使用方法

GPS.gcj_encrypt("纬度","经度"); // 函数返回转换后的高德坐标

代码实现

var GPS = { PI : 3.14159265358979324, x_pi : 3.14159265358979324 * 3000.0 / 180.0, delta : function (lat, lon) { // Krasovsky 1940 // // a = 6378245.0, 1/f = 298.3 // b = a * (1 - f) // ee = (a^2 - b^2) / a^2; var a = 6378245.0; // a: 卫星椭球坐标投影到平面地图坐标系的投影因子。 var ee = 0.00669342162296594323; // ee: 椭球的偏心率。 var dLat = this.transformLat(lon - 105.0, lat - 35.0); var dLon = this.transformLon(lon - 105.0, lat - 35.0); var radLat = lat / 180.0 * this.PI; var magic = Math.sin(radLat); magic = 1 - ee * magic * magic; var sqrtMagic = Math.sqrt(magic); dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * this.PI); dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * this.PI); return {'lat': dLat, 'lon': dLon}; }, //GPS---高德 gcj_encrypt : function ( wgsLat , wgsLon ) { if (this.outOfChina(wgsLat, wgsLon)) return {'lat': wgsLat, 'lon': wgsLon}; var d = this.delta(wgsLat, wgsLon); return {'lat' : wgsLat + d.lat,'lon' : wgsLon + d.lon}; }, outOfChina : function (lat, lon) { if (lon < 72.004 || lon > 137.8347) return true; if (lat < 0.8293 || lat > 55.8271) return true; return false; }, transformLat : function (x, y) { var ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x)); ret += (20.0 * Math.sin(6.0 * x * this.PI) + 20.0 * Math.sin(2.0 * x * this.PI)) * 2.0 / 3.0; ret += (20.0 * Math.sin(y * this.PI) + 40.0 * Math.sin(y / 3.0 * this.PI)) * 2.0 / 3.0; ret += (160.0 * Math.sin(y / 12.0 * this.PI) + 320 * Math.sin(y * this.PI / 30.0)) * 2.0 / 3.0; return ret; }, transformLon : function (x, y) { var ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x)); ret += (20.0 * Math.sin(6.0 * x * this.PI) + 20.0 * Math.sin(2.0 * x * this.PI)) * 2.0 / 3.0; ret += (20.0 * Math.sin(x * this.PI) + 40.0 * Math.sin(x / 3.0 * this.PI)) * 2.0 / 3.0; ret += (150.0 * Math.sin(x / 12.0 * this.PI) + 300.0 * Math.sin(x / 30.0 * this.PI)) * 2.0 / 3.0; return ret; } };