Finding nearby large city with geonames

Question

I have a simple php function which get's the closest nearby city from a given latitude and longitude:

function findCity($lat, $lng, $username) {
        $json_url = "http://api.geonames.org/findNearbyPlaceNameJSON?lat=" . $lat . "&lng=" . $lng . "&username=" . $username;
        $json = file_get_contents($json_url);
        $json = str_replace('},

            ]', "}

            ]", $json);
        $data = json_decode($json);

        echo "<pre>";
    print_r($data);
    echo "</pre>";
    } 

This method returns the following with lat: 51.992 and long: 4.89

stdClass Object
(
    [geonames] => Array
        (
            [0] => stdClass Object
                (
                    [countryName] => Netherlands
                    [adminCode1] => 11
                    [fclName] => city, village,...
                    [countryCode] => NL
                    [lng] => 4.876389
                    [fcodeName] => populated place
                    [distance] => 1.42349
                    [toponymName] => Langerak
                    [fcl] => P
                    [name] => Langerak
                    [fcode] => PPL
                    [geonameId] => 2751924
                    [lat] => 51.931667
                    [adminName1] => South Holland
                    [population] => 0
                )

        )

)

This returns the closest city, but I am looking for something like this. Where only the closest large city is returned. Is this possible? Or are there other alternatives to solve this. I've read about the Google Geocoding API, but we can't use it since we aren't using a Google map to show the results. (Note: the Geocoding API may only be used in conjunction with a Google map; geocoding results without displaying them on a map is prohibited. Source)

I know this isn't an actual programmer problem, but since the geonames forums are not really active, I figured I would post it here.

Answer 1

You need a list of the biggest cities. I didn't find an api call on geonames (maybe try freebase api for sorting by city relevance). Because the example list you show is short an static you could hard code it? If so you could use something shown below:

/*
* Haversine formula
* from: http://rosettacode.org/wiki/Haversine_formula#PHP
*/ 

class POI {
    private $latitude;
    private $longitude;
    public function __construct($latitude, $longitude) {
        $this->latitude = deg2rad($latitude);
        $this->longitude = deg2rad($longitude);
    }
    public function getLatitude() {return $this->latitude;}
    public function getLongitude(){return $this->longitude;}
    public function getDistanceInMetersTo(POI $other) {
        $radiusOfEarth = 6371000;// Earth's radius in meters.
        $diffLatitude = $other->getLatitude() - $this->latitude;
        $diffLongitude = $other->getLongitude() - $this->longitude;
        $a = sin($diffLatitude / 2) * sin($diffLatitude / 2) +
            cos($this->latitude) * cos($other->getLatitude()) *
            sin($diffLongitude / 2) * sin($diffLongitude / 2);
        $c = 2 * asin(sqrt($a));
        $distance = $radiusOfEarth * $c;
        return $distance;
    }
}


class bigcity
{
    public $name;
    public $lat;
    public $long;

    function __construct($name,$lat,$long)
    {
        $this->name=$name;
        $this->lat=$lat;
        $this->long=$long;
    }       
}   

function getbigcities()
{
    $bigcities = array();
    $bigcities[] = new bigcity('Amsterdam',52.374 ,4.89);
    $bigcities[] = new bigcity('Eindhoven',51.441 ,5.478);
    $bigcities[] = new bigcity('Groningen',53.219 ,6.567);
    return $bigcities;
}   


function findCity($lat, $lng)
{
    $userinput = new POI($lat,$lng);
    $bigcities = getbigcities();
    $distance = 1000000000;
    $result = '';
    foreach ($bigcities as $bigcity)
    {

        $delta = $userinput->getDistanceInMetersTo(new POI($bigcity->lat,$bigcity->long));
        if($delta<$distance)
        {
            $result = $bigcity->name;
            $distance = $delta;
        }   
    }   

    return ($result);
}   

echo findcity(51.556,5.091); //tilburg
echo findcity(52.55,6.15); //leeuwaarden
echo findcity(52.091,5.122); //utrecht
exit;