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Documentation Index

Fetch the complete documentation index at: https://algolia.com/llms.txt

Use this file to discover all available pages before exploring further.

In this tutorial, you’ll learn how to filter results around a polygonal location. This location can either be set manually or taken from the current user position. To run the code examples on this page, install the latest API client.

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Dataset

The guide uses a dataset of the 3,000+ biggest airports in the world.
JSON
[
 {
    "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, the latitude and longitude must be stored in the _geoloc attribute.

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Initialize the client

  1. Download the data set
  2. Set up an API client and send your data to Algolia

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Configure index settings

Even if you just want to sort by distance to a location, your textual relevance should also be good so that users can refine the search with a query. To do that, you must configure the . The searchable attributes are: name, city, country, and iata_code. 
var response = await client.SetSettingsAsync(
  "INDEX_NAME",
  new IndexSettings
  {
    SearchableAttributes = new List<string> { "name", "country", "city", "iata_code" },
    CustomRanking = new List<string> { "desc(links_count)" },
  }
);

​
Filtering inside a polygonal area

The USA can be considered as a polygon: Screenshot of a map showing the United States with a polygonal filter drawn over it, highlighting a specific region. To filter inside this rectangle, you need to pass the latitude and longitude of all the points to the insidePolygon parameter:
  • 42.01,-124.31,
  • 48.835509470063045,-124.40453125000005
  • 45.01082951668149,-65.95726562500005
  • 31.247243545293433,-81.06578125000004
  • 25.924152577235226,-97.68234374999997
  • 32.300311895879545,-117.54828125
The empty query ('') returns all matching airports. 
var response = await client.SearchSingleIndexAsync<Hit>(
  "INDEX_NAME",
  new SearchParams(
    new SearchParamsObject
    {
      InsidePolygon = new List<List<Double>>
      {
        new List<Double>
        {
          42.01,
          -124.31,
          48.835509470063045,
          -124.40453125000005,
          45.01082951668149,
          -65.95726562500005,
          31.247243545293433,
          -81.06578125000004,
          25.924152577235226,
          -97.68234374999997,
          32.300311895879545,
          -117.54828125,
        },
      },
    }
  )
);
Last modified on March 16, 2026