I'm using MongoDB to store about 1 million documents representing regions.
Each document contains a coordinates record in the following format
"coordinates" : {
"longitude" : -77.02687,
"latitude" : 38.888565
}
Given a set of coordinates { x, y }, what query should I run to find the region ( document ) that is closest to it?
Based on the MongoDB geospatial-queries documentation the answer is quite simple.
In order to query for locations near a region you should follow these steps
Step 1
Create an index on the location field
db.places.createIndex( { location: "2dsphere" } )
Step 2
Find regions close to { -73.9667, 40.78 } ordered by closest locations
db.places.aggregate( [
{
$geoNear: {
near: { type: "Point", coordinates: [ -73.9667, 40.78 ] },
spherical: true,
query: { category: "Parks" },
distanceField: "calcDistance"
}
}
] )
Related
i noticed that mongoDB $near and $geoNear returns around 1km bigger distance than should be.
Point1 (current location):
lat: 54.8985,
long: 23.9036,
Point2 (location in DB):
"location" : {
"type" : "Point",
"coordinates" : [
54.91689,
23.97423
]
}
based on multiple libraries distance should be around 4.7KM
however mongodb returns: "calcDistance" : 8082 = 8km
DIFFERENCE is 4 KM!
You can check it here:
I have tried both spherical and non-spehrical and tried both $geowNear and $near
my code:
db.getCollection('collection').aggregate([
{
$geoNear: {
near: { type: 'Point', coordinates: [ 54.8985, 23.9036 ] },
distanceField: 'calcDistance',
maxDistance: 5 * 1000,
}
}
])
Any ideas why?
Look slike $near and $geoNear need lat and long swapped. That was a problem.
Refer to this: geoNear returns incorrect distance
I have a location collection, and have used this code that shows location near the assigned geo location below:
db.location.find({ll:{$near:[-80.12996, 25.79315]}}).limit(5).pretty()
However, now I need to expand from this and find the top 5 pizza restaurant (field is type: "Pizza"), and ordered by the geo location above (need to use near to have it by ascending). Can't figure out how to do it. I tried to use aggregate but not working for me, I might have it in the wrong order or something.
step 1: create an index of the field with have location.
db.location.createIndex( { <location field> : "2dsphere" } )
step 2: try this query replacing your coordinates in lat lng:
db.location.aggregate([
{
$geoNear: {
near: { type: "Point", coordinates: [lat, lng]},
maxDistance:1000,
distanceField: "dist.calculated",
spherical: true
}
},
{
$match: {
type: "Pizza",
}
},
{
$sort: {
'dist.calculated': 1
}
},
{
$limit : 5
}
])
In my application I would like to query items that are close by (e.g. within 5km) to a coordinate and I tried to use $near to achieve that. With a quick look I thought it worked but after I tested it further it seems the query is somewhat inaccurate. Here is my setup:
I selected 2 coordinates that are a bit less than 5km apart from each other:
61.4644750214197, 23.8426943813556
61.497133399999996, 23.778528100000003
(At least according to tools like this, this or this the distance between those coordinates should be about ~4,99km)
I added one of the coordinates into empty "items" collection:
db.items.insert({
"geo" : {
"type" : "Point",
"coordinates" : [
61.4644750214197,
23.8426943813556
]
}
});
I added "2dsphere" index to the collection make geospatial queries possible:
db.items.createIndex( { geo : "2dsphere" } )
Finally, I used the other coordinate with $near query:
db.items.find({geo: {
$near: {
$geometry: {
type: "Point" ,
coordinates: [ 61.497133399999996, 23.778528100000003 ]
},
$maxDistance: 5000 // according to docs with '2dsphere' index and GeoJSON this is is meters
}
}}).count()
I expected the result to be 1 but instead it is 0. Even if I set $maxDistance to 7000 the result is still 0, but if I set it to 8000 the result will be 1.
Am I doing something wrong or are MongoDB geospatial queries (or just $near query?) that inaccurate? If so, is there a better way to get accurate results for this kind of query? This is my first time dealing with geospatial queries in MongoDB so there is probably a trivial explanation for my problem.
EDIT:
Basically I was dreaming of a functionality to show all items in map within X kilometres from users current location and X could be determined by user. It would be awkward if an item within 5km would not be visible even when the user wants to filter items within 7km.
I have tried most of the options for doing this query, like $centerSphere, $nearSphere and geoNear with similar results. They all seem to claim that the distance between my earlier mentioned coordinates is somewhere between 7-8km. I'm starting to think either 1. I'm missing some key peace of information about how distances work in general or 2. it simply is not possible to solve my problem with mongodb. Below are my queries for the other options:
$centerSphere (0 results with 5, 6 and 7km but 1 result with 8km):
db.items.find( { geo: {
$geoWithin: { $centerSphere: [ [ 61.497133399999996, 23.778528100000003 ], 5/6378.1 ]
}
}}).count()
geoNear (0 results with maxDistance 5000, 6000 and 7000 but 1 result with 8000):
db.runCommand(
{
geoNear: "items",
near: { type: "Point", coordinates: [ 61.497133399999996, 23.778528100000003 ] },
spherical: true,
maxDistance: 5000
}
)
I understand I am late to the party, but for all those who are facing similar issue
The problem here is that when you store that data into "coordinates", it must be in the [longitude, latitude] order because this is how mongodb works. https://docs.mongodb.com/manual/geospatial-queries/#spherical I just ran your example with reversed order of coordinates and it worked as expected.
db.items.insert({
"geo" : {
"type" : "Point",
"coordinates" : [
23.8426943813556,
61.4644750214197
]
}
});
And then i ran
db.items.find({geo: {
$near: {
$geometry: {
type: "Point" ,
coordinates: [ 23.778528100000003 , 61.497133399999996]
},
$maxDistance: 5000
}
}}).count()
The count here is 1:
Hope it helps
I have a collection "machine" with document
{
"_id" : "ac9d1db9-6a0d-47c6-97d3-a613c8dd0031",
"pin" : {
"machine":"test1",
"position" : [
-1.5716,
54.7732
]
}
}
Note: -1.5716 is lng and 54.7732 is lat
I have created a 2dsphere index on the document
db.machine.createIndex( { 'pin.position' : "2dsphere" } )
I try with 2 different versions of query (only difference in query is the near field in geoNear pipeline stage)
Query 1:
db.machine.aggregate(
[
{
"$geoNear":{
"near": [-0.2129092,51.5031594],
"limit":100,
"maxDistance":500*1000,
"distanceField": "dist.calculated",
"includeLocs": "dist.location",
"distanceMultiplier":1/1000,
"spherical": true
}
}
]
)
Note: -0.2129092 is lng and 51.5031594 is lat
Query 2
db.machine.aggregate(
[
{
"$geoNear":{
"near": { type: "Point", coordinates: [-0.2129092,51.5031594] },
"limit":100,
"maxDistance":500*1000,
"distanceField": "dist.calculated",
"includeLocs": "dist.location",
"distanceMultiplier":1/1000,
"spherical": true
}
}
]
)
Note: -0.2129092 is lng and 51.5031594 is lat
Query 1 returns me the document and provides that this document is 5.88161133560063e-05 Kms away from the search co-ordinates
Query 2 returns me the document and provides that this document is 375.135052595944 Kms away from the search co-ordinates
I cross-verify the distance between these lng/lat on a site http://andrew.hedges.name/experiments/haversine/ and see that the distance between the document and the search co-ordinates is around 374.835 Kms
It seems Query 2 is providing the correct result but am not sure as to what is the difference between Query 1 and Query 2 and if I am using it incorrectly.
Please advise
Query 1 provides the distance in legacy co-ordinate pairs and Query 2 provices the distance in meters (GeoJSON) and hence both queries are using different units
Please check the following link https://jira.mongodb.org/browse/SERVER-16652?jql=text%20~%20%22geoNear%22
I would like to have a MongoDB collection and each document contains a geospatial polygon defined by latitude/longitude points (in GeoJSON). Then, I would like to take any given longitude/latitude point and check if it resides within any of the MongoDB polygons defined in the documents. Hypothetically, this is what the documents would look like.
{
"type" : "congressional",
"points" : [
{ "coords" : [
-141.0205,
70.0187 ]
},
...
{ "coords" : [
-141.0205,
70.0187 ]
}
]
}
Or maybe like so:
{ loc :
{ type : "Polygon" ,
coordinates : [ [ [ 0 , 0 ] , [ 3 , 6 ] , [ 6 , 1 ] , [ 0 , 0 ] ] ]
} }
And then I would query it, hypothetically, like so (most likely with Mongo's $geoWithin):
db.places.find( { loc : { $geoWithin : { $geometry : "EACH DOCUMENT IN COLLECTION"} } } )
Is geofencing, or something similar, possible to do with the current MongoDB feature-set? If so, how would it be done?
I believe you would have to first find every document from the collection., and then make a "$geoWithin" query for every document, passing in the Polygon to test against for each case.
Depending on the number of documents in your collection, that may or may not provide sufficient performance.
MongoDB has full support for geofencing or finding documents whose geometry intersects with a given geometry (point, polygon). The query below is an example. geometry of Collection is the field containing the geometry.
Document Example:
{ "geometry": {
"type": "Polygon",
"coordinates": [
[
[
-74.001487,
40.692346
],
[
-74.001755,
40.692057
],
[
-74.000977,
40.691951
],
[
-74.000827,
40.692297
],
[
-74.001487,
40.692346
]
]
]
}
}
JS Query:
//find quests bots that matches the users location
await Collection.find({ geometry:
{ $geoIntersects:
{
{
type: "Point",
coordinates: [
-73.99460599999999,
40.7347229
]
}
}
}
});