public function get(D\Calculator\CalculatorInterface $calculator = null, D\Converter\ConverterInterface $unit_converter = null) {
        if (is_null($calculator)) {
            $calculator = new D\Calculator\Vincenty;
        }

        $distance = $calculator->calculate($this->point1, $this->point2);

        if (!is_null($unit_converter)) {
            $distance = $unit_converter->convert($distance);
        }
        return $distance;
    }