Filter results inside a rectangle

Use Algolia’s geo search capabilities to filter results inside a rectangle.

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

Dataset

The dataset contains 3000+ of the 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, 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

csharp

SearchClient client = new SearchClient("YourApplicationID", "YourWriteAPIKey");
SearchIndex index = client.InitIndex("your_index_name");

Configure Index Settings

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.

First, let’s configure the index.

go

res, err := index.SetSettings(search.Settings{
	SearchableAttributes: opt.SearchableAttributes(
		"name",
		"city",
		"country",
		"iata_code",
	),
	CustomRanking: opt.CustomRanking("desc(links_count)"),
})

Searchable attributes

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

Custom Ranking

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

Filtering inside a rectangle area

Let’s filter inside the United State of America. The USA can be considered as a rectangle:

To filter inside this rectangle we need the upper-left and bottom-right latitude and longitude:

• 49.067996905313834, 65.73828125
• 25.905859247243498, 128.8046875

We are going to use the insideBoundingBox parameter:

go

boundingBox := [][4]float64{
	{
		49.067996905313834, // p1Lat
		65.73828125,        // p1Lng
		25.905859247243498, // p2Lat
		128.8046875,        // p2Lng
	},
}

res, err := index.Search("", opt.InsideBoundingBox(boundingBox))

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