public function unit($symbol, $string = false)
    {
        // Format instance's meter value and factor to the specified unit.
        $m    = number_format($this->m, static::$s, '.', '');
        $fact = number_format(static::factorToMeters($symbol), static::$s, '.',
          '');

        // Divide the meters by the factor and trim end of zeros
        $unit = bcdiv($m, $fact, static::$s);
        $unit = static::removeTrailingZeros($unit);

        // Return rounded double value, or string value.
        return $string ? $unit : round($unit, 20);
    }