wg2Mars.js

/**
 * 引用不同的数据，会得到不同的地图切片
 * 卫星（无地标） WGS-84 一般 GCJ-02
 * <script src="https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false"></script>
 * 卫星（有地标） GCJ-02 一般 GCJ-02
 * <script src="https://ditu.google.cn/maps/api/js?v=3.exp&sensor=false"></script>
 */
(function (map) {

    var Converter = function () {
        this.PI = Math.PI;
        //
        // Krasovsky 1940
        //
        // a = 6378245.0, 1/f = 298.3
        // b = a * (1 - f)
        // ee = (a^2 - b^2) / a^2;
        this.a = 6378245.0;
        this.ee = 0.00669342162296594323;
    };
    Converter.prototype = {
        /**
         * World Geodetic System ==> Mars Geodetic System
         * WGS-84 ==> GCJ-02
         * 直接纠偏转换，部分地区，如较高海拔，可能会造成较大的误差
         * @param worldCoords include{latitude:value,longitude: value}
         * @returns marsCoords include{latitude: value,longitude: value}
         */
        toMars: function (worldCoords) {
            var marsCoords = {
//                latitude: 0,
//                longitude: 0
            };
            if (this.isOnEarth(worldCoords)) {
                marsCoords.latitude = worldCoords.latitude;
                marsCoords.longitude = worldCoords.longitude;
                return marsCoords;
            }

            var dLat = this.transformLat(worldCoords.longitude - 105.0, worldCoords.latitude - 35.0);
            var dLon = this.transformLon(worldCoords.longitude - 105.0, worldCoords.latitude - 35.0);
            var radLat = worldCoords.latitude / 180.0 * this.PI;
            var magic = Math.sin(radLat);
            magic = 1 - this.ee * magic * magic;

            var sqrtMagic = Math.sqrt(magic);

            dLat = (dLat * 180.0) / ((this.a * (1 - this.ee)) / (magic * sqrtMagic) * this.PI);
            dLon = (dLon * 180.0) / (this.a / sqrtMagic * Math.cos(radLat) * this.PI);

            marsCoords.latitude = worldCoords.latitude + dLat;
            marsCoords.longitude = worldCoords.longitude + dLon;


            return marsCoords;
        },
        /**
         * GCJ-02 ==> WGS-84
         * 反推，假设 GCJ-02 就是 WGS-84，计算大概差值，精度不高，
         * 二分法查表内插可能会好点，但是太多数据，前端不好做
         * @param marsCoords include{latitude:value,longitude: value}
         * @returns worldCoords include{latitude: value,longitude: value}
         */
        toEarth: function (marsCoords) {
            var worldCoords = {
//                latitude: 0,
//                longitude: 0
            }, marsTemp, dLat, dLon;

            marsTemp = this.toMars(marsCoords);

            dLat = marsTemp.latitude - marsCoords.latitude;
            dLon = marsTemp.longitude - marsCoords.longitude;

            worldCoords.latitude = marsCoords.latitude - dLat;
            worldCoords.longitude = marsCoords.longitude - dLon;

            return worldCoords;
        },
        isOnEarth: function (worldCoords) {
            return (worldCoords.longitude < 72.004 || worldCoords.longitude > 137.8347 || worldCoords.latitude < 0.8293 || worldCoords.latitude > 55.8271);
        },
        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;
        },
        /**
         * GCJ-02 ==> BD-09
         * 木有验证过 三角函数转换后计算误差本来就有点蛋疼
         * @param marsCoords include{latitude:value,longitude: value}
         * @returns baiduCoords include{latitude: value,longitude: value}
         */
        marsToBaidu: function (marsCoords) {
            var baiduCoords = {
//                latitude: 0,
//                longitude: 0
            };

            var x = marsCoords.longitude,
                y = marsCoords.latitude,
                z, theta, x_pi;

            x_pi = this.PI * 3000.0 / 180.0;
            z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * x_pi);
            theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * x_pi);

            baiduCoords.latitude = z * Math.sin(theta) + 0.006;
            baiduCoords.longitude = z * Math.cos(theta) + 0.0065;

            return baiduCoords;

        },
        /**
         * BD-09 ==> GCJ-02
         * 木有验证过 三角函数转换后计算误差本来就有点蛋疼
         * @param baiduCoords include{latitude:value,longitude: value}
         * @returns marsCoords include{latitude: value,longitude: value}
         */
        baiduToMars: function (baiduCoords) {
            var marsCoords = {
//                latitude: 0,
//                longitude: 0
            };
            var x = baiduCoords.longitude - 0.0065, y = baiduCoords.latitude - 0.006,
                z, theta, x_pi;

            x_pi = this.PI * 3000.0 / 180.0;
            z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * x_pi);
            theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * x_pi);

            marsCoords.latitude = z * Math.sin(theta);
            marsCoords.longitude = z * Math.cos(theta);

            return marsCoords;
        }

    };

    map.converter = new Converter();

})(window.map);