iOS2个坐标之间的距离

// 计算两坐标之间的距离

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double distanceWithcoord(double lon1,double lat1,double lon2,double lat2)

{

    double er = 6378137;

    double radlat1 = PI*lat1/180.0f;

    double radlat2 = PI*lat2/180.0f;

    double radlong1 = PI*lon1/180.0f;

    double radlong2 = PI*lon2/180.0f;

    if( radlat1 < 0 ) radlat1 = PI/2 + fabs(radlat1);// south

    if( radlat1 > 0 ) radlat1 = PI/2 - fabs(radlat1);// north

    if( radlong1 < 0 ) radlong1 = PI*2 - fabs(radlong1);//west

    if( radlat2 < 0 ) radlat2 = PI/2 + fabs(radlat2);// south

    if( radlat2 > 0 ) radlat2 = PI/2 - fabs(radlat2);// north

    if( radlong2 < 0 ) radlong2 = PI*2 - fabs(radlong2);// west

    double x1 = er * cos(radlong1) * sin(radlat1);

    double y1 = er * sin(radlong1) * sin(radlat1);

    double z1 = er * cos(radlat1);

    double x2 = er * cos(radlong2) * sin(radlat2);

    double y2 = er * sin(radlong2) * sin(radlat2);

    double z2 = er * cos(radlat2);

    double d = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)+(z1-z2)*(z1-z2));

    double theta = acos((er*er+er*er-d*d)/(2*er*er));

    double dist  = theta*er;

    return dist;

}