GPS获取坐标 显示Google map偏差计算

用手机获取GPS坐标 显示在手机地图偏差大约在100-200米左右，我把坐标放在 Maps.google.com 搜索坐标定位则相当精确。

可能是.....为了安全吧故意加的偏差

不过可以计算偏差使位置精确

代码如下

public class EvilTransform {

     static double  pi = 3.14159265358979324;

     static double a = 6378245.0;

     static double ee = 0.00669342162296594323;

     public static double mgLat;

     public static double mgLon;

    public static void transform( double wgLat, double wgLon)

    {

        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 = Math.sin(radLat);

        magic = 1 - ee * magic * magic;

        double sqrtMagic = Math. sqrt(magic);

        dLat = (dLat * 180.0) / (( a * (1 - ee)) / (magic * sqrtMagic) * pi);

        dLon = (dLon * 180.0) / ( a / sqrtMagic * Math.cos(radLat) * pi);

        mgLat = wgLat + dLat;

        mgLon = wgLon + dLon;

    }

    static Boolean 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;

    }

    static 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 * Math.sqrt(Math.abs(x));

        ret += (20.0 * Math. sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;

        ret += (20.0 * Math. sin(y * pi) + 40.0 * Math.sin(y / 3.0 * pi)) * 2.0 / 3.0;

        ret += (160.0 * Math. sin(y / 12.0 * pi) + 320 * Math.sin(y * pi / 30.0)) * 2.0 / 3.0;

        return ret;

    }

    static double transformLon( double x, double y)

    {

        double 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 * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;

        ret += (20.0 * Math. sin(x * pi) + 40.0 * Math.sin(x / 3.0 * pi)) * 2.0 / 3.0;

        ret += (150.0 * Math. sin(x / 12.0 * pi) + 300.0 * Math.sin(x / 30.0 * pi)) * 2.0 / 3.0;

        return ret;

    }

}