火星座標與地球座標的轉換，以及地球上兩點之間的距離計算

火星座標與地球座標的轉換，以及地球上兩點之間的距離計算

1. 地球座標就是我們通過GPS獲得的GPS座標，而我們所謂的火星座標，就是經過國家測繪局進行加密後的座標（WGS-84 ），而這個火星座標只在國內有效。

下面這個函數用來判斷座標是否屬於中國境內，但是這個座標判斷不是太準確，只是大概判斷。

        bool outOfChina(double lat, double lon){
            if (lon < 72.004 || lon > 137.8347)
                return true;
            if (lat < 0.8293 || lat > 55.8271)
                return true;
            return false;
        }

1. 地球座標轉火星座標,

        double transformLat(double x, double y)
        {
            double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * System.Math.Sqrt(System.Math.Abs(x));
            ret += (20.0 * System.Math.Sin(6.0 * x * pi) + 20.0 * System.Math.Sin(2.0 * x * pi)) * 2.0 / 3.0;
            ret += (20.0 * System.Math.Sin(y * pi) + 40.0 * System.Math.Sin(y /3.0 * pi)) * 2.0 / 3.0;
            ret += (160.0 * System.Math.Sin(y / 12.0 * pi) + 320 * System.Math.Sin(y * pi / 30.0)) * 2.0 / 3.0;
            return ret;
        }

        double transformLon(double x, double y)
        {
            double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * System.Math.Sqrt(System.Math.Abs(x));
            ret += (20.0 * System.Math.Sin(6.0 * x * pi) + 20.0 * System.Math.Sin(2.0 * x * pi)) * 2.0 / 3.0;
            ret += (20.0 * System.Math.Sin(x * pi) + 40.0 * System.Math.Sin(x / 3.0 * pi)) * 2.0 / 3.0;
            ret += (150.0 * System.Math.Sin(x / 12.0 * pi) + 300.0 * System.Math.Sin(x / 30.0 * pi)) * 2.0 / 3.0;
            return ret;
        }  


 /** 
     * 地球座標轉換爲火星座標 
     * World Geodetic System ==> Mars Geodetic System 
     * 
     * @param wgLat  地球座標 
     * @param wgLon 
     * 
     * mglat,mglon 火星座標 
     */
    void transform2Mars(double wgLat, double wgLon, out double mgLat, out double mgLon)  
    {
        if (outOfChina(wgLat, wgLon) )  
        {  
            mgLat  = wgLat;  
            mgLon = wgLon;  
            return ;  
        }  
        double dLat = transformLat(wgLon - 105.0, wgLat - 35.0);  
        double dLon = transformLon(wgLon - 105.0, wgLat - 35.0);  
        double radLat = wgLat / 180.0 * pi;  
        double magic = System.Math.Sin(radLat);  
        magic = 1 - ee * magic * magic;  
        double sqrtMagic = System.Math.Sqrt(magic);  
        dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);  
        dLon = (dLon * 180.0) / (a / sqrtMagic * System.Math.Cos(radLat) * pi);  
        mgLat = wgLat + dLat;  
        mgLon = wgLon + dLon;  
    }

1. 火星座標轉地球座標

public PointLatLng Mar2Earth(PointLatLng Mar) {
         PointLatLng Earth = new PointLatLng();
         if (outOfChina(Mar.Lat, Mar.Lng))
         {
            return Mar;
         }
        PointLatLng tmp;
        double initDelta = 0.1;
        double threshold = 0.000001;
        double dLat = initDelta, dLon = initDelta;
        double mLat = Mar.Lat - dLat, mLon = Mar.Lng - dLon;
        double pLat = Mar.Lat + dLat, pLon = Mar.Lng + dLon;
        double wgsLat, wgsLon, i = 0;
        double lastDlat = initDelta, lastDlng = initDelta;
        PointLatLng lasttmp = new PointLatLng((mLat + pLat) / 2, (mLon + pLon) / 2);
        PointLatLng minitemp=new PointLatLng();

        while (true) {
            wgsLat = (mLat + pLat) / 2;
            wgsLon = (mLon + pLon) / 2;
transform2Mars(wgsLat,wgsLon,tmp.Lat.tmp.lng);

            dLat = tmp.Lat - Mar.Lat;
            dLon = tmp.Lng - Mar.Lng;

            if ((System.Math.Abs(dLat) < threshold) && (System.Math.Abs(dLon) < threshold))
                break;

            if (dLat + dLon >= lastDlat + lastDlng)
            {
            }
            else {
                lastDlat = dLat;
                lastDlng = dLon;

                minitemp.Lat = tmp.Lat;
                minitemp.Lng = tmp.Lng;
            }

            if (lasttmp.Lat == tmp.Lat && lasttmp.Lng == tmp.Lng) {
                wgsLat = minitemp.Lat;
                wgsLon = minitemp.Lng;

                break;
            }
            lasttmp = tmp;

            if (dLat > 0) pLat = wgsLat; else mLat = wgsLat;
            if (dLon > 0) pLon = wgsLon; else mLon = wgsLon;


           if (++i > 10000) break;
        }

        if(i>=10000){
            return new PointLatLng();
        }
        Earth.Lat = wgsLat;
        Earth.Lng = wgsLon;
        return Earth;
     }

火星座標轉地球座標這個函數其實是利用地球座標轉火星座標方法使用二分法求得，精度爲：threshold = 0.000001

1. 求地球上兩點之間的距離

      public  double Distance(double lat1, double lon1, double lat2, double lon2)
        {
            double latitude1, longitude1, latitude2, longitude2;
            double dlat, dlon;
            latitude1 = lat1;
            longitude1 = lon1;
            latitude2 = lat2;
            longitude2 = lon2;
            //computing procedure  
            double a, c, distance;
            dlon = System.Math.Abs((longitude2 - longitude1)) * System.Math.PI / 180;
            dlat = System.Math.Abs((latitude2 - latitude1)) * System.Math.PI / 180;
            a = (System.Math.Sin(dlat / 2) * System.Math.Sin(dlat / 2)) + System.Math.Cos(latitude1 * System.Math.PI / 180) * System.Math.Cos(latitude2 * System.Math.PI / 180) * (System.Math.Sin(dlon / 2) * System.Math.Sin(dlon / 2));
            if (a == 1.0)
                c = System.Math.PI;
            else
                c = 2 * System.Math.Atan(System.Math.Sqrt(a) / System.Math.Sqrt(1 - a));
            distance = 6378137.0 * c;

            return distance;
        }