Mongoid Geospatial

A Mongoid Extension that simplifies the use of MongoDB spatial features.

** On beta again **

Removing some trash, improving and adding support for RGeo and GeoRuby. Version 2+ is going to be beta testing, when it's ready I'll release v3, So the major version stays the same as mongoid.

There are no plans to support MongoDB < 2.0 There are no plans to support Mongoid <= 2.0

Quick Start

This gem focus on (making helpers for) spatial features MongoDB has. You can also use an external Geometric/Spatial alongside.

# 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

  # If your are going to query on your points, don't forget to index:
  spatial_index :location
  # You can index points with :spatial => true option too, see below.
end

For geo points, an extra macro geo_field is available

class Place
  include Mongoid::Document
  include Mongoid::Geospatial

  # field :location, type: Point, spatial: true
  geo_field :location
end

Generate indexes on MongoDB:

rake db:mongoid:create_indexes

Index programatically via https://github.com/kristianmandrup/mongoid_indexing gem

Mongoid::Indexing.create_indexes

This is fx useful when running specs or when working with spatials on a gem or engine.

Points

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
  • 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 *only works in ruby 1.9 and up because hashes below ruby 1.9 because they are not ordered
  • anything with the a method #to_xy or #to_lng_lat that converts itself to [long, lat] array

We store data in the DB as a [x, y] array then reformat when it is returned to you

hudson = River.create(
  name: 'Hudson',
  length: 315,
  discharge: 21_400,
  # when setting array LNG (x) MUST BE FIRST LAT (y) MUST BE SECOND
  # source: [-73.935833,44.106667],
  # but we can use hash in any order
  source: {:lat => 44.106667, :lng => -73.935833},
  mouth: {:latitude => 40.703056, :longitude => -74.026667}

Now to access this spatial information we can do this

hudson.mouth  # => [-74.026667, 40.703056]

If you need a hash

hudson.mouth.to_hsh  # => { x: -74.026667, y: 40.703056 }

If you are using GeoRuby or RGeo

hudson.mouth.to_geo  # => NiceGeolib::Point

Conventions: This lib uses #x and #y everywhere. 1. It's shorter than lat or lng or another variation that also confuses. 2. 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. In the eyes of a moralist it's not even a valid position point, it does not have #z or #m.

Distance and other geometrical calculations are delegated to the external library you choosed. More info about using RGeo or GeoRuby below. Some built in helpers for mongoid queries:

# Returns middle point + radius
# Useful to search #within_circle
hudson.mouth.radius(5)        # [[-74.., 40..], 5]
hudson.mouth.radius_sphere(5) # [[-74.., 40..], 0.00048..]

# Returns hash if needed
hudson.mounth.to_hsh              # {:x => -74.., :y => 40..}
hudson.mounth.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

Query

Before you read about mongoid_spatial have sure you read this:

http://mongoid.org/en/origin/docs/selection.html#standard

All MongoDB queries are handled by Mongoid.

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_box

    • Bar.within_box(location: hood.area)

  • within_circle

    • Bar.within_circle(location: hood.area)

  • within_circle_sphere

    • Bar.within_circle_sphere(location: hood.area)

  • within_polygon

    • Bar.within_polygon(location: city.area)

External Libraries

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/geo_ruby

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.

Use Nothing?

This lib won't stand in your way. Write your own wrapper if you want.

Geometry Helpers

We currently support GeoRuby and RGeo. If you require one of those, a #to_geo method will be available to all spatial fields, returning the external library corresponding object. To illustrate:

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_geo.class # RGeo::Geographic::SphericalPointImpl

Configure

Assemble it as you need (use a initializer file):

With RGeo

Mongoid::Geospatial.use_rgeo
# Optional
# Mongoid::Geospatial.factory = RGeo::Geographic.spherical_factory

With GeoRuby

Mongoid::Geospatial.use_georuby

Defaults (change if you know what you're doing)

Mongoid::Geospatial.lng_symbol = :x
Mongoid::Geospatial.lat_symbol = :y
Mongoid::Geospatial.earth_radius = EARTH_RADIUS

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

  # spatial indexing
  spatial_index :mouth

  # default mongodb options
  spatial_index :mouth, {bit: 24, min: -180, max: 180}

  # query by location
  spatial_scope :location
end

Helpers

You can use :spatial => true to add an '2d' index automatically, No need for spatial_index :location:

field :location,  type: Point, :spatial => 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_box
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..]

Mongo DB 1.9+ New Geo features

Multi-location Documents v.1.9+

MongoDB now also supports indexing documents by multiple locations. These locations can be specified in arrays of sub-objects, for example:

> db.places.insert({ addresses : [ { name : "Home", loc : [55.5, 42.3] }, { name : "Work", loc : [32.3, 44.2] } ] })
> db.places.ensureIndex({ "addresses.loc" : "2d" })

Multiple locations may also be specified in a single field:

> db.places.insert({ lastSeenAt : [ { x : 45.3, y : 32.2 }, [54.2, 32.3], { lon : 44.2, lat : 38.2 } ] })
> db.places.ensureIndex({ "lastSeenAt" : "2d" })

By default, when performing geoNear or $near-type queries on collections containing multi-location documents, the same document may be returned multiple times, since $near queries return ordered results by distance. Queries using the $within operator by default do not return duplicate documents.

v2.0 In v2.0, this default can be overridden by the use of a $uniqueDocs parameter for geoNear and $within queries, like so:

> db.runCommand( { geoNear : "places" , near : [50,50], num : 10, uniqueDocs : false } )
> db.places.find( { loc : { $within : { $center : [[0.5, 0.5], 20], $uniqueDocs : true } } } )

Currently it is not possible to specify $uniqueDocs for $near queries Whether or not uniqueDocs is true, when using a limit the limit is applied (as is normally the case) to the number of results returned (and not to the docs or locations). If running a geoNear query with uniqueDocs : true, the closest location in a document to the center of the search region will always be returned - this is not true for $within queries.

In addition, when using geoNear queries and multi-location documents, often it is useful to return not only distances, but also the location in the document which was used to generate the distance. In v2.0, to return the location alongside the distance in the geoNear results (in the field loc), specify includeLocs : true in the geoNear query. The location returned will be a copy of the location in the document used.

If the location was an array, the location returned will be an object with "0" and "1" fields in v2.0.0 and v2.0.1.

> db.runCommand({ geoNear : "places", near : [ 0, 0 ], maxDistance : 20, includeLocs : true })
{
  "ns" : "test.places",
  "near" : "1100000000000000000000000000000000000000000000000000",
  "results" : [
    {
      "dis" : 5.830951894845301,
      "loc" : {
        "x" : 3,
        "y" : 5
      },
      "obj" : {
        "_id" : ObjectId("4e52672c15f59224bdb2544d"),
        "name" : "Final Place",
        "loc" : {
          "x" : 3,
          "y" : 5
        }
      }
    },
    {
      "dis" : 14.142135623730951,
      "loc" : {
        "0" : 10,
        "1" : 10
      },
      "obj" : {
        "_id" : ObjectId("4e5266a915f59224bdb2544b"),
        "name" : "Some Place",
        "loc" : [
          [
            10,
            10
          ],
          [
            50,
            50
          ]
        ]
      }
    },
    {
      "dis" : 14.142135623730951,
      "loc" : {
        "0" : -10,
        "1" : -10
      },
      "obj" : {
        "_id" : ObjectId("4e5266ba15f59224bdb2544c"),
        "name" : "Another Place",
        "loc" : [
          [
            -10,
            -10
          ],
          [
            -50,
            -50
          ]
        ]
      }
    }
  ],
  "stats" : {
    "time" : 0,
    "btreelocs" : 0,
    "nscanned" : 5,
    "objectsLoaded" : 3,
    "avgDistance" : 11.371741047435734,
    "maxDistance" : 14.142157540259815
  },
  "ok" : 1
}

The plan is to include this functionality in a future release. Please help out ;)

This Fork

This fork is not backwards compatible with 'mongoid_spatial'. This fork delegates calculations to the external libs and use Moped.

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

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

Using mongoid_geospatial (or mongoid for that matter) without rails?

https://github.com/kristianmandrup/mongoid_indexing

You need a way to create indexes easily, check out the gem above.

Thanks

  • Thanks to Kristian Mandrup for creating the base of the gem and a few of the tests
  • Thanks to CarZen LLC. for letting me release the code we are using

Contributing

  • Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
  • Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
  • Fork the project
  • Start a feature/bugfix branch
  • Commit and push until you are happy with your contribution
  • Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
  • Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

WTFPL

http://en.wikipedia.org/wiki/WTFPL