Awesome
Mongoid Geospatial
A Mongoid Extension that simplifies the use of MongoDB spatial features.
Quick Start
This gem focuses on (making helpers for) MongoDB's spatial features using Mongoid 5, 6 and 7.
# Gemfile
gem 'mongoid-geospatial'
A Place
to illustrate Point
, Line
and Polygon
class Place
include Mongoid::Document
# Include the module
include Mongoid::Geospatial
# Just like mongoid,
field :name, type: String
# define your field, but choose a geometry type:
field :location, type: Point
field :route, type: LineString
field :area, type: Polygon
# To query on your points, don't forget to index:
# You may use a method:
sphere_index :location # 2dsphere
# or
spatial_index :location # 2d
# Or use a helper directly on the `field`:
field :location, type: Point, spatial: true # 2d
# or
field :location, type: Point, sphere: true # 2dsphere
end
Generate indexes on MongoDB via rake:
rake db:mongoid:create_indexes
Or programatically:
Place.create_indexes
Points
This gem defines a specific Point
class under the Mongoid::Geospatial namespace. Make sure to use type: ::Mongoid::Geospatial::Point
to avoid name errors or collisions with other Point
classes you might already have defined NameError
s.
Currently, MongoDB supports query operations on 2D points only, so that's what this lib does. All geometries apart from points are just arrays in the database. Here's is how you can input a point as:
- longitude latitude array in that order - [long,lat] ([x, y])
- an unordered hash with latitude key(:lat, :latitude) and a longitude key(:lon, :long, :lng, :longitude)
- an ordered hash with longitude as the first item and latitude as the second item; this hash does not have include the latitude and longitude keys
- anything with the a method #to_xy or #to_lng_lat that converts itself to [long, lat] array
Note: the convention of having longitude as the first coordinate may vary for other libraries. For instance, Google Maps often refer to "LatLng". Make sure you keep those differences in mind. See below for how to configure this library for LatLng.
We store data in the DB as a [x, y] array then reformat when it is returned to you
cafe = Place.create(
name: 'Café Rider',
location: {:lat => 44.106667, :lng => -73.935833},
# or
location: {latitude: 40.703056, longitude: -74.026667}
#...
Now to access this spatial information we can do this
cafe.location # => [-74.026667, 40.703056]
If you need a hash
cafe.location.to_hsh # => { x: -74.026667, y: 40.703056 }
If you are using GeoRuby or RGeo
cafe.location.to_geo # => GeoRuby::Point
cafe.location.to_rgeo # => RGeo::Point
Conventions:
This lib uses #x and #y everywhere. It's shorter than lat or lng or another variation that also confuses. A point is a 2D mathematical notation, longitude/latitude is when you use that notation to map an sphere. In other words: all longitudes are 'xs' where not all 'xs' are longitudes.
Distance and other geometrical calculations are delegated to the external library of your choice. More info about using RGeo or GeoRuby below. Some built in helpers for mongoid queries:
# Returns middle point + radius
# Useful to search #within_circle
cafe.location.radius(5) # [[-74.., 40..], 5]
cafe.location.radius_sphere(5) # [[-74.., 40..], 0.00048..]
# Returns hash if needed
cafe.location.to_hsh # {:x => -74.., :y => 40..}
cafe.location.to_hsh(:lon, :lat) # {:lon => -74.., :lat => 40..}
And for polygons and lines:
house.area.bbox # Returns polygon bounding_box (envelope)
house.area.center # Returns calculate middle point
Model Setup
You can create Point, Line, Circle, Box and Polygon on your models:
class CrazyGeom
include Mongoid::Document
include Mongoid::Geospatial
field :location, type: Point, spatial: true, delegate: true
field :route, type: Line
field :area, type: Polygon
field :square, type: Box
field :around, type: Circle
# default mongodb options
spatial_index :location, {bit: 24, min: -180, max: 180}
# query by location
spatial_scope :location
end
Helpers
You can use spatial: true
to add a '2d' index automatically,
No need for spatial_index :location
:
field :location, type: Point, spatial: true
And you can use sphere: true
to add a '2dsphere' index automatically, no need for spatial_sphere :location
:
field :location, type: Point, sphere: true
You can delegate some point methods to the instance itself:
field :location, type: Point, delegate: true
Now instead of instance.location.x
you may call instance.x
.
Nearby
You can add a spatial_scope
on your models. So you can query:
Bar.nearby(my.location)
instead of
Bar.near(location: my.location)
Good when you're drunk. Just add to your model:
spatial_scope :<field>
Geometry
You can also store Circle, Box, Line (LineString) and Polygons. Some helper methods are available to them:
# Returns a geometry bounding box
# Useful to query #within_geometry
polygon.bbox
polygon.bounding_box
# Returns a geometry calculated middle point
# Useful to query for #near
polygon.center
# Returns middle point + radius
# Useful to search #within_circle
polygon.radius(5) # [[1.0, 1.0], 5]
polygon.radius_sphere(5) # [[1.0, 1.0], 0.00048..]
Query
Before you proceed, make sure you have read this:
http://mongoid.github.io/old/en/origin/docs/selection.html#standard
All MongoDB queries are handled by Mongoid/Origin.
http://www.rubydoc.info/github/mongoid/origin/Origin/Selectable
You can use Geometry instance directly on any query:
- near
Bar.near(location: person.house)
Bar.where(:location.near => person.house)
- near_sphere
Bar.near_sphere(location: person.house)
Bar.where(:location.near_sphere => person.house)
- within_polygon
Bar.within_polygon(location: [[[x,y],...[x,y]]])
# or with a bbox
Bar.within_polygon(location: street.bbox)
- intersects_line
- intersects_point
- intersects_polygon
External Libraries
We currently support GeoRuby and RGeo. If you require one of those, a #to_geo and #to_rgeo, respectivelly, method(s) will be available to all spatial fields, returning the external library corresponding object.
Use RGeo?
https://github.com/dazuma/rgeo
RGeo is a Ruby wrapper for Proj/GEOS. It's perfect when you need to work with complex calculations and projections. It'll require more stuff installed to compile/work.
Use GeoRuby?
https://github.com/nofxx/georuby
GeoRuby is a pure Ruby Geometry Library. It's perfect if you want simple calculations and/or keep your stack in pure ruby. Albeit not full featured in maths it has a handful of methods and good import/export helpers.
Example
class Person
include Mongoid::Document
include Mongoid::Geospatial
field :location, type: Point
end
me = Person.new(location: [8, 8])
# Example with GeoRuby
point.class # Mongoid::Geospatial::Point
point.to_geo.class # GeoRuby::SimpleFeatures::Point
# Example with RGeo
point.class # Mongoid::Geospatial::Point
point.to_rgeo.class # RGeo::Geographic::SphericalPointImpl
Configure
Assemble it as you need (use a initializer file):
With RGeo
Mongoid::Geospatial.with_rgeo!
# Optional
# Mongoid::Geospatial.factory = RGeo::Geographic.spherical_factory
With GeoRuby
Mongoid::Geospatial.with_georuby!
By default the convention of this library is LngLat, configure it for LatLng as follows.
Mongoid::Geospatial.configure do |config|
config.point.x = Mongoid::Geospatial.lat_symbols
config.point.y = Mongoid::Geospatial.lng_symbols
end
You will need to manually migrate any existing Point
data if you change configuration in an existing system.
This Fork
This fork is not backwards compatible with 'mongoid_spacial'. This fork delegates calculations to external libs.
Change in your models:
include Mongoid::Spacial::Document
to
include Mongoid::Geospatial
And for the fields:
field :source, type: Array, spacial: true
to
field :source, type: Point, spatial: true # or sphere: true
Beware the 't' and 'c' issue. It's spaTial.
Troubleshooting
Mongo::OperationFailure: can't find special index: 2d
Indexes need to be created. Execute command:
rake db:mongoid:create_indexes
Programatically
Model.create_indexes
Contributing
See CONTRIBUTING.
License
Copyright (c) 2009-2017 Mongoid Geospatial Authors
MIT License, see MIT-LICENSE.