MongoDB print distance between two points

Question

When I am firing this query on MongoDB, I am getting all the places in the proximity of 500 miles to the specified co-ordinates. But I want to know the exact distance between the specified co-ordinates and the result location.

db.new_stores.find({ "geometry": { $nearSphere: { $geometry: { type: "Point", coordinates: [ -81.093699, 32.074673 ] }, $maxDistance: 500 * 3963 } } } ).pretty()

My Output looks like:

{
    "_id" : ObjectId("565172058bc200b0db0f75b1"),
    "type" : "Feature",
    "geometry" : {
        "type" : "Point",
        "coordinates" : [
            -80.148826,
            25.941116
        ]
    },
    "properties" : {
        "Name" : "Anthony's Coal Fired Pizza",
        "Address" : "17901 Biscayne Blvd, Aventura, FL"
    }
}

I also want to know the distance of this place from the specified co-ordinate. I created 2dsphere index on geometry.

Solution 1

You can use the $geoNear aggregate pipeline stage to produce a distance from the queried point:

 db.new_stores.aggregate([
    { "$geoNear": {
        "near": {
            "type": "Point",
            "coordinates": [ -81.093699, 32.074673 ]
        }, 
        "maxDistance": 500 * 1609,
        "spherical": true,
        "distanceField": "distance",
        "distanceMultiplier": 0.000621371
    }}
]).pretty()

This allows you to specify "distanceField" which will produce another field in the output documents containing the distance from the queried point. You can also use "distanceMultiplier" to apply any conversion to the output distance as required ( i.e meters to miles, and noting that all GeoJSON distances are returned in meters )

There is also the geoNear command with similar options, but it of course does not return a cursor as output.

Solution 2

MongoDB provides a $geoNear aggregator for calculating the distance of documents in a collection with GeoJson coordinates.

Let us understand it with a simple example. Consider a simple collection shops

1. Create Collection

db.createCollection('shops')

2. Insert documents in shops collections

db.shops.insert({name:"Galaxy store",address:{type:"Point",coordinates:[28.442894,77.341299]}})

db.shops.insert({name:"A2Z store",address:{type:"Point",coordinates:[28.412894,77.311299]}})

db.shops.insert({name:"Mica store",address:{type:"Point",coordinates:[28.422894,77.342299]}})

db.shops.insert({name:"Full Stack developer",address:{type:"Point",coordinates:[28.433894,77.334299]}})

3. create GeoIndex on "address" fields

db.shops.createIndex({address: "2dsphere" } )

4. Now use a $geoNear aggregator to find out the documents with distance.

db.shops.aggregate([{$geoNear:{near:{type:"Point",coordinates:[28.411134,77.331801]},distanceField: "shopDistance",$maxDistance:150000,spherical: true}}]).pretty()

Here coordinates:[28.411134,77.331801] is the center position or quired position from where documents will be fetched.

distanceField:"shopDistance" , $geoNear Aggregator return shopDistance as fields in result.

Result:

{ "_id" : ObjectId("5ef047a4715e6ae00d0893ca"), "name" : "Full Stack developer", "address" : { "type" : "Point", "coordinates" : [ 28.433894, 77.334299 ] }, "shopDistance" : 621.2848190449148 }
{ "_id" : ObjectId("5ef0479e715e6ae00d0893c9"), "name" : "Mica store", "address" : { "type" : "Point", "coordinates" : [ 28.422894, 77.342299 ] }, "shopDistance" : 1203.3456146763526 }
{ "_id" : ObjectId("5ef0478a715e6ae00d0893c7"), "name" : "Galaxy store", "address" : { "type" : "Point", "coordinates" : [ 28.442894, 77.341299 ] }, "shopDistance" : 1310.9612119555288 }
{ "_id" : ObjectId("5ef04792715e6ae00d0893c8"), "name" : "A2Z store", "address" : { "type" : "Point", "coordinates" : [ 28.412894, 77.311299 ] }, "shopDistance" : 2282.6640175038788 }

Here shopDistance will be in meter.

Comments

[work_in_progress]

Thanks a lot, it is working perfectly. Curious to know why did you multiply it by 1609?

[Blakes Seven]

@SiMemon Because there are 1609 meters in a mile, and vice/versa on the distanceMultiplier. The 3963 number you were using is the conversion of "radians" to miles, which when used with GeoJSON point coordinates would be incorrect. Radians are only used with both storage and query are using "legacy coordinate pairs".

[Dileep Paul]

Can we find distance from queried point to multiple geopoints in same query instead of one?

[Admin]

Could this determine if two circles intersect? That is, suppose I have a collection which contains a latitude and longitude, as well as a radius. Since GeoJSON does not support circles, could I write a query to determine the distance between two points, and then check if that distance is less than the sum of both radii? Would that work and would it be performant? Thanks.