public function getRoughDistance($clientLng, $clientLat, $poiLng, $poiLat)
    {
        $result = abs($clientLng - $poiLng) + abs($clientLat - $poiLat);
        $this->BackyardError->log(5, "client({$clientLng}, {$clientLat}) poi({$poiLng}, {$poiLat}) roughDistance = {$result}");
        return $result;
    }