Mongo

Find Nearest Locations With MongoDB — How To?

There are many ways to implement finding nearest locations by given latitude and longitude .

Some of the implementations can be achieved through a backend logic,

and the other ways can be done by utilizing some features(Spatial Indexes) provided by DBMSs’(Mysql, SQL, MongoDB,….etc).

In this post I will explain by example how we can do it with MongoDB.

What are Latitude and Longitude? , You can find more from here https://www.latlong.net/

How To ?

Let’s create a collection in MongoDb and we call it locations .

To Achieve the query of finding nearest locations by given latitude and longitude, we do the following Steps:

First Step : Each stored document must follow a structure called GeoJSON .

Second Step : We have to create 2dsphere Index in that collection .

Third Step : We run the Find query! .

First Step: GeoJSON

The locations collection will store a list of documents, each one of them represents a location(or an address) on the map.

Each document will follow this example/structure:

{
  "country": "UAE",
  "city": "Dubai",
  "address": "Dubai Mall",
  "loc": {
    "type": "Point",
    "coordinates": [
      25.1973,//latitude
      55.2793 //longitude
    ]
  }
}

This Structure is following GeoJSON Structure!

— What’s GeoJSON Structure?

It is a JSON document that must have an object inside it , as follows :

<field>: { type: <GeoJSON type> , coordinates: <coordinates> }

Projection on the previous (Dubai Mall) document :

"loc" : {"type" : "Point" , "coordinates" : [25.1973,55.2793]}

Read more about : GeoJSON Object https://docs.mongodb.com/manual/reference/geojson/

Ok, Great!, till now we’ve created locations collection that has a list of documents that follow GeoJSON structure, so let’s suppose we have those documents inside locations:

Second Step : Index Creation

We need to run createIndex Command to tell MongoDb that this collection is following the GeoJSON structure, so we can achieve the query of finding nearest locations successfully.

Command syntax:

db.collection.createIndex( { <location field> : "2dsphere" } )

Projection:

db.locations.createIndex( { "loc" : "2dsphere" } )

Third Step : Find Query

As Per MongoDb documentation, here is the syntax of finding nearest locations by given latitude/longitude:

db.collection.find(
{
   <location field>: {
     $near: {
       $geometry: {
          type: "Point" ,
          coordinates: [ <longitude> , <latitude> ]
       },
     }
   }
})

If I want to get the nearest locations to my current location, I should provide my current latitude/longitude, so let’s suppose

My Current Latitude: 25.087626 / Longitude: 55.151134 . (Dubai Marina)

So when I query the collection, we do:

db.locations.find(
{
   "loc": {
     $near: {
       $geometry: {
          type: "Point" ,
          coordinates: [ 25.087626 , 55.151134 ]
       },
     }
   }
})

Query Result: (ordered by nearest, according to my Latitude :25.087626/Longitude : 55.151134)

This is it!, Hope you find this information useful!

db.collectionname.find({
    "location": {
        $near: {
            $geometry:
                { type: "Point", coordinates: [50.0, -0.1330] }, $maxDistance: 500
        }
    }
})

db.address.find ({
  location: {
     $near: {
       $geometry: {
          type: "Point" ,
          coordinates: [ -72.7738706,41.6332836 ]
       },
       $maxDistance: 4,
       $minDistance: 0
     }
   }
})