75 lines
2.2 KiB
JavaScript
75 lines
2.2 KiB
JavaScript
/**
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* 判断坐标是否在中国境外
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*/
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function outOfChina(lng, lat) {
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return (
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lng < 72.004 || lng > 137.8347 ||
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lat < 0.8293 || lat > 55.8271
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);
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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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const PI = 3.1415926535897932384626;
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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 * 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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const PI = 3.1415926535897932384626;
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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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* WGS84 转 GCJ-02（火星坐标系）
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*/
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export const wgs84ToGcj02 = function(lng, lat){
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const PI = 3.1415926535897932384626;
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const a = 6378245.0; // 长半轴
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const ee = 0.00669342162296594323; // 扁率
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// 不在中国境内的坐标不转换
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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 mglat = lat + dlat;
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const mglng = lng + dlng;
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return [mglng, mglat];
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}
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export const getDistance = function(lat1, lng1, lat2, lng2) {
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const R = 6371000;
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const dLat = (lat2 - lat1) * Math.PI / 180;
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const dLng = (lng2 - lng1) * Math.PI / 180;
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const a =
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0.5 - Math.cos(dLat)/2 +
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Math.cos(lat1 * Math.PI / 180) *
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Math.cos(lat2 * Math.PI / 180) *
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(1 - Math.cos(dLng))/2;
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return R * 2 * Math.asin(Math.sqrt(a));
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} |