New in version 12.0.0.
Geospatial data, or "geodata", specifies points and geometric objects on the Earth's surface. With the geodata types, you can create queries that check whether a given point is contained within a shape. For example, you can find all coffee shops within 15Â km of a specified point.
Changed in version realm@12.3.0: Geospatial data supported in Atlas Device Sync
Realm.js v12.3.0 and later adds support for geospatial data in Atlas Device Sync. This allows you to subscribe to geospatial queries in a synced realm. If you try to subscribe to a geospatial query with an older version of the SDK, you will receive a server error with a compensating write. For more information about managing your Sync subscriptions, refer to Geospatial - React Native SDK.
For more information on querying geospatial data with Device Sync, refer to Geospatial Data in the App Services documentation.
The SDK supports geospatial queries using the following data types:
GeoPoint
GeoCircle
GeoBox
GeoPolygon
The SDK provides these geospatial data types to simplify querying geospatial data. You cannot persist these data types directly.
For information on how to persist geospatial data, refer to the Persist Geospatial Data section on this page.
To query against geospatial data, you can use the geoWithin operator with RQL. The geoWithin operator takes the coordinates property of an embedded object that defines the point we're querying, and one of the geospatial shapes to check if that point is contained within the shape.
The format for querying geospatial data is the same, regardless of the shape of the geodata region.
A GeoPoint defines a specific location on the Earth's surface. All of the geospatial data types use GeoPoints to define their location.
GeoPoint can be one of three types:
An object with:
latitude: a number value
longitude: a number value
altitude: an optional number value
CanonicalGeoPoint: an interface that satisfies the GeoJSON specifications for a point
GeoPosition: an array with longitude, latitude, and an optional altitude
A GeoPoint is used only as a building block of the other shapes: GeoCircle, GeoBox, and GeoPolygon. These shapes, and the GeoPoint type, are used in queries, not for persistance.
To save geospatial data to realm, refer to Persist Geospatial Data on this page.
A GeoCircle defines a circle on the Earth's surface. You define a GeoCircle by providing:
A GeoPoint for the center of the circle
A number for the distance (radius) of the circle
The radius distance uses radians as the unit of measure. The SDK provides the methods kmToRadians and miToRadians to convert kilometers or miles to radians.
The following code shows two examples of creating a circle:
import React from 'react';import {View, Text} from 'react-native';import {GeoCircle, GeoPoint, kmToRadians} from 'realm';import {useQuery} from '@realm/react';function Geocircle(): JSX.Element { const smallCircle: GeoCircle = { center: [-121.9, 47.3], distance: 0.004363323, }; const radiusFromKm = kmToRadians(44.4); const largeCircleCenter: GeoPoint = { longitude: -122.6, latitude: 47.8, }; const largeCircle: GeoCircle = { center: largeCircleCenter, distance: radiusFromKm, }; const companiesInSmallCircle = useQuery( Company, collection => collection.filtered('location geoWithin $0', smallCircle), [smallCircle], ); const companiesInLargeCircle = useQuery( Company, collection => collection.filtered('location geoWithin $0', largeCircle), [largeCircle], ); return ( <View> <Text>Small circle: {companiesInSmallCircle.length}</Text> <Text>Large circle: {companiesInLargeCircle.length}</Text> </View> );}The following image shows the results of creating two objects: a small circle and a large circle.
Queries against geospatial data return realm objects within the shapes you define. From the example above, this is the result of our queries:
A GeoBox defines a rectangle on the Earth's surface. You define the rectangle by specifying the bottom left (southwest) corner and the top right (northeast) corner. A GeoBox behaves in the same way as the corresponding GeoPolygon.
The following example creates 2 boxes:
import React from 'react';import {View, Text} from 'react-native';import {GeoBox, GeoPoint} from 'realm';import {useQuery} from '@realm/react';function Geobox(): JSX.Element { const largeBox: GeoBox = { bottomLeft: [-122.7, 47.3], topRight: [-122.1, 48.1], }; const smallBoxBottomLeft: GeoPoint = { longitude: -122.4, latitude: 47.5, }; const smallBoxTopRight: GeoPoint = { longitude: -121.8, latitude: 47.9, }; const smallBox: GeoBox = { bottomLeft: smallBoxBottomLeft, topRight: smallBoxTopRight, }; const companiesInLargeBox = useQuery( Company, collection => collection.filtered('location geoWithin $0', largeBox), [largeBox], ); const companiesInSmallBox = useQuery( Company, collection => collection.filtered('location geoWithin $0', smallBox), [smallBox], ); return ( <View> <Text>Small box: {companiesInSmallBox.length}</Text> <Text>Large box: {companiesInLargeBox.length}</Text> </View> );}The following image shows the results of creating two objects: a small box and a large box.
Queries against geospatial data return realm objects within the shapes you define. From the example above, this is the result of our queries:
A GeoPolygon defines a polygon on the Earth's surface. Because a polygon is a closed shape, you must provide a minimum of 4 points: 3 points to define the polygon's shape, and a fourth to close the shape.
ImportantThe fourth point in a polygon must be the same as the first point.
You can also exclude areas within a polygon by defining one or more "holes". A hole is another polygon whose bounds fit completely within the outer polygon. The following example creates 3 polygons: one is a basic polygon with 5 points, one is the same polygon with a single hole, and the third is the same polygon with two holes:
import React from 'react';import {View, Text} from 'react-native';import {GeoPolygon, GeoPoint} from 'realm';import {useQuery} from '@realm/react';function Geopolygon(): JSX.Element { const basicPolygon: GeoPolygon = { outerRing: [ [-122.8, 48.0], [-121.8, 48.2], [-121.6, 47.6], [-122.0, 47.0], [-122.6, 47.2], [-122.8, 48.0], ], }; const outerRing: GeoPoint[] = [ [-122.8, 48.0], [-121.8, 48.2], [-121.6, 47.6], [-122.0, 47.0], [-122.6, 47.2], [-122.8, 48.0], ]; const hole: GeoPoint[] = [ [-122.6, 47.8], [-122.2, 47.7], [-122.6, 47.4], [-122.5, 47.6], [-122.6, 47.8], ]; const polygonWithOneHole: GeoPolygon = { outerRing: outerRing, holes: [hole], }; const hole2: GeoPoint[] = [ { longitude: -122.05, latitude: 47.55, }, { longitude: -121.9, latitude: 47.55, }, { longitude: -122.1, latitude: 47.3, }, { longitude: -122.05, latitude: 47.55, }, ]; const polygonWithTwoHoles: GeoPolygon = { outerRing: outerRing, holes: [hole, hole2], }; const companiesInBasicPolygon = useQuery( Company, collection => collection.filtered('location geoWithin $0', basicPolygon), [basicPolygon], ); const companiesInPolygonWithTwoHoles = useQuery( Company, collection => collection.filtered('location geoWithin $0', polygonWithTwoHoles), [polygonWithTwoHoles], ); return ( <View> <Text>Basic polygon: {companiesInBasicPolygon.length}</Text> <Text> Polygon with two holes: {companiesInPolygonWithTwoHoles.length} </Text> </View> );}The following image shows the results of creating three objects: a polygon, a polygon with one hole, and a polygon with two holes.
Queries against geospatial data return realm objects within the shapes you define. From the example above, this is the result of our queries:
Important Cannot Persist Geospatial Data TypesCurrently, you can only persist geospatial data. Geospatial data types cannot be persisted directly. For example, you can't declare a property that is of type GeoBox.
These types can only be used as arguments for geospatial queries.
If you want to persist geospatial data, it must conform to the GeoJSON spec .
To create a class that conforms to the GeoJSON spec, you:
Create an embedded realm object. For more information about embedded objects, refer to Embedded Objects - React Native SDK.
At a minimum, add the two fields required by the GeoJSON spec:
A field of type double[] that maps to a "coordinates" (case sensitive) property in the realm schema.
A field of type string that maps to a "type" property. The value of this field must be "Point".
To simplify geodata persistance, you can define a model that implements CanonicalGeoPoint, which already has the correct shape. The following example shows an embedded class named MyGeoPoint that is used to persist geospatial data.
You then use the custom MyGeoPoint class in your realm model, as shown in the following example. You add instances of your class to the realm just like any other Realm model. However, in this example, because the MyGeoPoint class does not extend Realm.Object, we must specify MyGeoPoint.schema when opening the realm:
import React from 'react';import Realm, {ObjectSchema, CanonicalGeoPoint, GeoPosition} from 'realm';import {RealmProvider} from '@realm/react';class MyGeoPoint implements CanonicalGeoPoint { coordinates!: GeoPosition; type = 'Point' as const; constructor(long: number, lat: number) { this.coordinates = [long, lat]; } static schema: ObjectSchema = { name: 'MyGeoPoint', embedded: true, properties: { type: 'string', coordinates: 'double[]', }, };}class Company extends Realm.Object<Company> { _id!: number; location!: MyGeoPoint; static schema: ObjectSchema = { name: 'Company', properties: { _id: 'int', location: 'MyGeoPoint', }, primaryKey: '_id', };}export const Geospatial = () => { return ( <View> {/* `MyGeoPoint` does not extend `Realm.Object`, so you pass only the `.schema` when opening the realm. */} <RealmProvider schema={[Company, MyGeoPoint.schema]}> <WriteGeospatialObjects /> </RealmProvider> </View> );};Within RealmProvider, create your geospatial objects by combining the embedded class with classes that extend Realm.Object.
import React from 'react';import {View} from 'react-native';import {useEffect} from 'react';import {useRealm, useQuery} from '@realm/react';function WriteGeospatialObjects(): JSX.Element { const realm = useRealm(); const companies = useQuery(Company); useEffect(() => { if (!companies.length) { writeNewCompany({_id: 6, location: new MyGeoPoint(-122.35, 47.68)}); writeNewCompany({_id: 9, location: new MyGeoPoint(-121.85, 47.9)}); } }, []); type CompanyProps = { _id: number; location: MyGeoPoint; }; const writeNewCompany = ({_id, location}: CompanyProps) => { realm.write(() => { realm.create(Company, { _id, location, }); }); }; return ( <View> <Geocircle /> <Geobox /> <Geopolygon /> </View> );}The following image shows the results of creating these two company objects.
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