+(CGFloat)getDistanceFrom:(CLLocationCoordinate2D)from To:(CLLocationCoordinate2D)to
{
double EARTH_RADIUS = 6371393;//地球半径 单位米
CGFloat dis = sinf(from.latitude*M_PI/180)*sinf(to.latitude*M_PI/180)+cosf(from.latitude*M_PI/180)*cosf(to.latitude*M_PI/180)*cosf((from.longitude-to.longitude)*M_PI/180);
dis = EARTH_RADIUS*acosf(dis);
return dis;
}