public function exactDistanceFrom(LatLng $coord)
    {
        $lat1 = deg2rad($this->getLat());
        $lat2 = deg2rad($coord->getLat());
        $lon1 = deg2rad($this->getLng());
        $lon2 = deg2rad($coord->getLng());

        $dLatHalf = ($lat2 - $lat1) / 2;
        $dLonHalf = ($lon2 - $lon1) / 2;

        $a = pow(sin($dLatHalf), 2) + cos($lat1) * cos($lat2) * pow(sin($dLonHalf), 2);
        $c = 2 * atan2(sqrt($a), sqrt(1 - $a));

        return $c * UnitsType::EARTH_RADIUS;
    }