Guides / Managing results / Refine results / Geo location

Filter Results Around a Location

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In this tutorial, we’ll see how we can filter results around a location. This location can either be set manually or taken from the current user position.

Dataset# A

In this tutorial we’ll use a dataset of the 3000+ of the biggest airports in the world.

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[
 {
    "objectID": "3797",
    "name": "John F Kennedy Intl",
    "city": "New York",
    "country": "United States",
    "iata_code": "JFK",
    "_geoloc": {
      "lat": 40.639751,
      "lng": -73.778925
    },
    "links_count": 911
  }
]

To tell Algolia where each record is located, we need to have the latitude and longitude stored in the _geoloc attribute.

You can download the dataset here. Have look at how to import it in Algolia here.

Initialize the client# A

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// composer autoload
require __DIR__ . '/vendor/autoload.php';

// if you are not using composer
// require_once 'path/to/algoliasearch.php';

$client = \Algolia\AlgoliaSearch\SearchClient::create(
  'AJ0P3S7DWQ',
  '••••••••••••••••••••'
);

$index = $client->initIndex('your_index_name');

Configure Index Settings# A

Even if we want to sort by distance to a location we need the textual relevance to be good in case refine the search with a query.

For that lets configure the index.

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$index->setSettings([
  'searchableAttributes' => [
    'name',
    'city',
    'country',
    'iata_code'
  ],
  'customRanking' => [
    'desc(links_count)'
  ]
]);

Searchable attributes#

We’re going to search in our 4 textual attributes: name, city, country and iata_code.

Custom Ranking#

Lets use the number of other connected airports to any airport as a ranking metric. The more connection the better.

Ranking#

When filtering around a location, Algolia can also sort the results by distance from this location.

The sorting by distance happens in the criterion geo of the ranking formula. If you don’t have this criterion active, you cannot sort by distance.

Filtering around a given location# A

Let’s filter airports around New York City. New York City has a latitude of 40.71 and a longitude of -74.01.

We are going to use the aroundLatLng parameter.

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$results = $index->search('', [
  'aroundLatLng' => '40.71, -74.01'
]);

We are using the empty query ('') to tell that we want all airports

Filtering around the current user location# A

As we don’t know in advance the Lat/Lng coordinates of the current user, we can rely on the IP address that we’ll automatically associate to a location.

We are going to use the aroundLatLngViaIP parameter.

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/**
 * '94.228.178.246' should be replaced with the actual IP you would like to search around.
 * Depending on your stack there are multiple ways to get this information.
 */

$ip = '94.228.178.246';

$results = $index->search('', [
  'aroundLatLngViaIP' => true,
  'X-Forwarded-For' => $ip
]);

Filtering Radius# A

By default the engine will define automatically a radius to filter on depending on the area density.

To define the radius ourselves we can use the aroundRadius parameter. The bigger it is the less filtering you have.

Let’s sort by distance to New York City, taking a radius of 1000 km.

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$results = $index->search('', [
  'aroundLatLng' => '40.71, -74.01'
  'aroundRadius' => 1000000 // 10000 km
]);

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