I have a documents contains list of location "boxes" (square area). Each box is represented by 2 points (bottom-left or south-west, top-right or north-east).
Document, for example:
{
locations: [
[[bottom,left],[top,right]],
[[bottom,left],[top,right]],
[[bottom,left],[top,right]]
]
}
I'm using 2d index for those boundaries points.
My input is a specific location point [x,y] and I want to fetch all documents that have at list one box that this point is located in it.
Is there any geospatial operator I can use to do that?
How do I write this query?
You can use the box operator, see:
http://docs.mongodb.org/manual/reference/operator/query/box/#op._S_box with the following example taken directly from that page:
db.places.find( { loc : { $geoWithin : { $box :
[ [ 0 , 0 ] ,
[ 100 , 100 ] ] } } } )
It is worth noting that the 2d index is considered legacy. If you can convert to using GeoJSON and a 2dsphere index, then you can use the $geoWithin operator: see
http://docs.mongodb.org/manual/reference/operator/query/geoWithin/#op._S_geoWithin
GeoJSON has a number of other benefits, not least of which, is that it is easily transmitted and digested by web mapping apps such as OpenLayers or Leaflet.
Related
I try to find a polygon intersecting a "Big" polygon inside a MongoDB document.
From the documentation I know that
For $geoIntersects, if you specify a single-ringed polygon that has an area greater than a single hemisphere, ... , $geoIntersects queries for the complementary geometry.
If the "Big" polygon is used in the query - you can specify a custom MongoDB CRS to avoid that:
$geometry: {
type: "Polygon",
coordinates: [ <coordinates> ],
crs: {
type: "name",
properties: { name: "urn:x-mongodb:crs:strictwinding:EPSG:4326"
}
}
But how can I handle it, if it's the other way around, the "Big" polygon is stored in the MongoDB ? Simple use case for the described scenario: Find all countries a polygon intersects
I am trying find a solution on how to display polygons that are only within a specific range, a circle with radius using leaflet.
Polygons screenshots
Before, I have ask for help regarding on the display of points within a specific range but this time, since a polygon have many nodes/coordinates, i don't have any idea of how it can be done for polygons; a foreach statement?
Any solution? Thanks for the help!
Similar problem solved for displaying points within a specific range
Since you're using MongoDB, the best solution here is (if that's possible), to handle this in the database. Put 2dsphere indexes on your document's loc field and use a $geoWithin query in combination with $centerSphere:
The following example queries grid coordinates and returns all documents within a 10 mile radius of longitude 88 W and latitude 30 N. The query converts the distance to radians by dividing by the approximate radius of the earth, 3959 miles:
db.places.find( {
loc: { $geoWithin: { $centerSphere: [ [ -88, 30 ], 10/3959 ] } }
} )
2dsphere reference: http://docs.mongodb.org/manual/core/2dsphere/
$geoWithin reference: http://docs.mongodb.org/manual/reference/operator/query/geoWithin/
$centerSphere reference: http://docs.mongodb.org/manual/reference/operator/query/centerSphere/
If you really want to do this clientside (which i absolutely wouldn't recommend) and you don't want to build your on solution (which is possible) you could take a look at GeoScript.
GeoScript's geom.Geometry() class has a contains method:
Tests if this geometry contains the other geometry (without boundaries touching).
Geom.geometry reference: http://geoscript.org/js/api/geom/geometry.html
EDIT: Here's the pure JS/Leaflet solution as requested in the comments, this is quick-n-dirty, but it should work. Here the containsPolygon method returns true when all of the polygon's points are within the circle:
L.Circle.include({
'containsPoint': function (latLng) {
return this.getLatLng().distanceTo(latLng) < this.getRadius();
},
'containsPolygon': function (polygon) {
var results = [];
polygon.getLatLngs().forEach(function (latLng) {
results.push(this.containsPoint(latLng));
}, this);
return (results.indexOf(false) === -1);
}
});
Here's a working example: http://plnkr.co/edit/JlFToy?p=preview
If you want to return true if one or more of the polygon's points are within the circle than you must change the return statement to this:
return (results.indexOf(true) !== -1);
Is there a way to find out what polygons (specifically circles) a specific Point lies in?
In this case I would have stored a documents containing circles, like below, I would pass in a latitude and longitude for a point, and would like to get back all documents where the point is within the given circle.
{
"_id" : ObjectId("53e3e85ce4b0c2e8227a1dad"),
"name" : "Menlo College",
"location" : [-122.1928, 37.45632],
"radius" : NumberLong(215),
},
{
"_id" : ObjectId("53e43d19e4b0aeabcb3d3f9d"),
"name" : "West Valley College",
"location" : [-122.01021194458008, 37.263226547586207],
"radius" : NumberLong(604),
}
If this is not possible, then is it at least possible with other GeoJSON shapes? Everything I've found so far indicates that the inverse is possible (find all points which like inside a circle), but nothing for this scenario.
Thanks
It is possible using MongoDB's $geoIntersects Geospatial query operator.
So, if you have a collection of GeoJson polygons and you want to find out all the polygons that intersect with your given point, then you need to run the following:
db.places.find( { <locationFieldOfYourDocuments> :
{ $geoIntersects :
{ $geometry :
{ type : "Point" ,
coordinates: [long, lat]
} } } } )
In the command above, loc is that attribute of each document that contains the coordinates for GeoJson polygon. Also, make sure that you have 2dsphere index over <locationFieldOfYourDocuments>.
Now, to get your original problem solved I will use a little bit of javascript. There may be better solutions but not in my knowledge.
Let's say all your circles are stored in Circles collection. I would query that collection and fetch each circle one by one and then perform an intersect with another collection that would contain a single point which would be the one you wanted to query if it intersects with the circles or not. So let the point be stored in SinglePoint collection.
The script would look like...
db.Intersections.remove({}); // emptying the output collection
var circleCursor = db.Circles.find();
while (circleCursor.hasNext()) {
var circle = circleCursor.next();
var coord = circle.location;
var radiusInRadians = circle.radius * conversionFactorForRadius;
var intersect = db.SinglePoint.find({loc :
{ $geoWithin :
{$centerSphere : [coord], radiusInRadians}
}});
if (intersect.hasNext()) {db.Intersections.add(circle)} // this will add all intersecting circles to Intersections collection
}
All you have to do is save this script in a file (myScript.js) and make a call:
mongo DBName pathTomyScript.js
This will store all the circles that intersect with your input point in the Intersects collection. All the above collections should be in DBName database.
I am trying to order at list by nearest place. This is working fine with this code:
Cloud.Places.query({
page: 1,
per_page: 20,
where: {
lnglat: { '$nearSphere': [latitudefast,longitudefast], }
},
order: {
lnglat: { '$nearSphere': [latitudefast,longitudefast], }
},
latitudefast and longitudefast is representing the actual position on the user. It has be defined before the query.
But it is "upside down", which means that the nearest place is in the bottom of the list, and the one farthest away is at the top of the list! How come? How do I order in reverse? Am i ordering wrong?
Thanks!
Have you tried not specifying the order? $nearSphere by default returns results sorted by distance.
From MongoDB's documentation (which ACS uses as its data store) describing $near:
The above query finds the closest points to (50,50) and returns them
sorted by distance (there is no need for an additional sort
parameter).
This applies to $nearSphere as well.
http://www.mongodb.org/display/DOCS/Geospatial+Indexing
I am trying to get my head around MongoDB and geospatial searches.
Basically what I want is for users to be able to query documents (images) that
are shot within a set distance from the users current location. So I the user is searching for all images that are shot within 1 km from where he is standing I try to use
the below example but I have no idea what to set as the maxdistance value.
db.places.find({ loc : { $near : [50,50] , $maxDistance : 5 }})
So my question is what do I set as maxdistance if I am searching for documents
within a 1 km radius?
I am totally stuck here.
In order to use mongodb $near queries with km bounds, you need to convert the radius value to km. By default mongodb $near accepts $maxDistance as radius.
Convert distance by 111.12 (one degree is approximately 111.12 kilometers) when using km, or leave distance as it is on using degree
to your question
what do I set as maxdistance if I am searching for documents within a
1 km radius?
you can use this
db.places.find( { loc : { $near : [50,50] , $maxDistance : 1/111.12 } } )
I have answered how to use mongo geospatial features here in detail. You can check out
Since version 2.4 of MongoDB you can specify the radius directly in meters as a value of $maxDistance, like this:
db.<collection>.find({loc: {$near :
{$geometry :
{
type: 'Point',
coordinates: [<longitude> , <latitude>]
}
},
$maxDistance: 10*100
}
});
In recent versions I am using Spring and Mongo 4.0.5. Important thing is type of index and location data type. I am using 2dsphere,org.springframework.data.mongodb.core.geo.GeoJsonPoint
Later on it generate corresponding mongo query with geometry with distance in meters.
{ "location" : { "$nearSphere" : { "$geometry" : { "type" : "Point", "coordinates" : [18.341772, 43.834183] }, "$maxDistance" : 331.0 }