73 lines
2.1 KiB
JavaScript
73 lines
2.1 KiB
JavaScript
/**
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* 高德地图坐标转换工具函数
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* GCJ-02 (火星坐标系) 转 WGS-84 (GPS坐标系)
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*/
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const PI = 3.14159265358979324;
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const a = 6378245.0; // 地球长半轴
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const ee = 0.00669342162296594323; // 扁率
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/**
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* 检查坐标是否在国外
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*/
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function outOfChina(lng, lat) {
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if (lng < 72.004 || lng > 137.8347) {
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return true;
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}
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if (lat < 0.8293 || lat > 55.8271) {
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return true;
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}
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return false;
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}
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/**
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* 纬度转换
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*/
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function transformLat(x, y) {
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let ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
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ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0;
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ret += (20.0 * Math.sin(y * PI) + 40.0 * Math.sin(y / 3.0 * PI)) * 2.0 / 3.0;
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ret += (160.0 * Math.sin(y / 12.0 * PI) + 320.0 * Math.sin(y * PI / 30.0)) * 2.0 / 3.0;
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return ret;
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}
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/**
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* 经度转换
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*/
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function transformLng(x, y) {
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let ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
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ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0;
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ret += (20.0 * Math.sin(x * PI) + 40.0 * Math.sin(x / 3.0 * PI)) * 2.0 / 3.0;
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ret += (150.0 * Math.sin(x / 12.0 * PI) + 300.0 * Math.sin(x / 30.0 * PI)) * 2.0 / 3.0;
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return ret;
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}
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/**
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* GCJ-02 转 WGS-84
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* @param {number} lng - GCJ-02经度
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* @param {number} lat - GCJ-02纬度
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* @returns {Array} [WGS-84经度, WGS-84纬度]
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*/
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export function gcj02ToWgs84(lng, lat) {
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// 检查是否在国内
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if (outOfChina(lng, lat)) {
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return [lng, lat];
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}
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let dLat = transformLat(lng - 105.0, lat - 35.0);
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let dLng = transformLng(lng - 105.0, lat - 35.0);
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const radLat = lat / 180.0 * PI;
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let magic = Math.sin(radLat);
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magic = 1 - ee * magic * magic;
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const sqrtMagic = Math.sqrt(magic);
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dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * PI);
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dLng = (dLng * 180.0) / (a / sqrtMagic * Math.cos(radLat) * PI);
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const wgsLat = lat - dLat;
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const wgsLng = lng - dLng;
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return [parseFloat(wgsLng.toFixed(6)), parseFloat(wgsLat.toFixed(6))];
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}
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