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README.md 31.52 KiB

Geocoder

Geocoder is a complete geocoding solution for Ruby. With Rails it adds geocoding (by street or IP address), reverse geocoding (find street address based on given coordinates), and distance queries. It's as simple as calling geocode on your objects, and then using a scope like Venue.near("Billings, MT").

Compatibility

  • Supports multiple Ruby versions: Ruby 1.8.7, 1.9.2, 1.9.3, and JRuby.
  • Supports multiple databases: MySQL, PostgreSQL, SQLite, and MongoDB (1.7.0 and higher).
  • Supports Rails 3.x. If you need to use it with Rails 2 please see the rails2 branch (no longer maintained, limited feature set).
  • Works very well outside of Rails, you just need to install either the json (for MRI) or json_pure (for JRuby) gem.

Installation

Install Geocoder like any other Ruby gem:

gem install geocoder

Or, if you're using Rails/Bundler, add this to your Gemfile:

gem "geocoder"

and run at the command prompt:

bundle install

Object Geocoding

ActiveRecord

Your model must have two attributes (database columns) for storing latitude and longitude coordinates. By default they should be called latitude and longitude but this can be changed (see "Model Configuration" below):

rails generate migration AddLatitudeAndLongitudeToModel latitude:float longitude:float
rake db:migrate

For reverse geocoding your model must provide a method that returns an address. This can be a single attribute, but it can also be a method that returns a string assembled from different attributes (eg: city, state, and country).

Next, your model must tell Geocoder which method returns your object's geocodable address:

geocoded_by :full_street_address   # can also be an IP address
after_validation :geocode          # auto-fetch coordinates

For reverse geocoding, tell Geocoder which attributes store latitude and longitude:

reverse_geocoded_by :latitude, :longitude
after_validation :reverse_geocode  # auto-fetch address

Mongoid

First, your model must have an array field for storing coordinates:

field :coordinates, :type => Array

You may also want an address field, like this:

field :address

but if you store address components (city, state, country, etc) in separate fields you can instead define a method called address that combines them into a single string which will be used to query the geocoding service.

Once your fields are defined, include the Geocoder::Model::Mongoid module and then call geocoded_by:

include Geocoder::Model::Mongoid
geocoded_by :address               # can also be an IP address
after_validation :geocode          # auto-fetch coordinates

Reverse geocoding is similar:

include Geocoder::Model::Mongoid
reverse_geocoded_by :coordinates
after_validation :reverse_geocode  # auto-fetch address

Once you've set up your model you'll need to create the necessary spatial indices in your database:

rake db:mongoid:create_indexes

Be sure to read Latitude/Longitude Order in the Notes on MongoDB section below on how to properly retrieve latitude/longitude coordinates from your objects.

MongoMapper

MongoMapper is very similar to Mongoid, just be sure to include Geocoder::Model::MongoMapper.

Mongo Indices

By default, the methods geocoded_by and reverse_geocoded_by create a geospatial index. You can avoid index creation with the :skip_index option, for example:

include Geocoder::Model::Mongoid
geocoded_by :address, :skip_index => true

Bulk Geocoding

If you have just added geocoding to an existing application with a lot of objects you can use this Rake task to geocode them all:

rake geocode:all CLASS=YourModel

Geocoder will print warnings if you exceed the rate limit for your geocoding service.

Request Geocoding by IP Address

Geocoder adds a location method to the standard Rack::Request object so you can easily look up the location of any HTTP request by IP address. For example, in a Rails controller or a Sinatra app:

# returns Geocoder::Result object
result = request.location

See Advanced Geocoding below for more information about Geocoder::Result objects.

Location-Aware Database Queries

To find objects by location, use the following scopes:

Venue.near('Omaha, NE, US', 20)    # venues within 20 miles of Omaha
Venue.near([40.71, 100.23], 20)    # venues within 20 miles of a point
Venue.geocoded                     # venues with coordinates
Venue.not_geocoded                 # venues without coordinates

With geocoded objects you can do things like this:

if obj.geocoded?
  obj.nearbys(30)                      # other objects within 30 miles
  obj.distance_from([40.714,-100.234]) # distance from arbitrary point to object
  obj.bearing_to("Paris, France")      # direction from object to arbitrary point
end

Some utility methods are also available:

# look up coordinates of some location (like searching Google Maps)
Geocoder.coordinates("25 Main St, Cooperstown, NY")
 => [42.700149, -74.922767]

# distance (in miles) between Eiffel Tower and Empire State Building
Geocoder::Calculations.distance_between([47.858205,2.294359], [40.748433,-73.985655])
 => 3619.77359999382

# find the geographic center (aka center of gravity) of objects or points
Geocoder::Calculations.geographic_center([city1, city2, [40.22,-73.99], city4])
 => [35.14968, -90.048929]

Please see the code for more methods and detailed information about arguments (eg, working with kilometers).

Distance and Bearing

When you run a location-aware query the returned objects have two attributes added to them (only w/ ActiveRecord):

  • obj.distance - number of miles from the search point to this object
  • obj.bearing - direction from the search point to this object

Results are automatically sorted by distance from the search point, closest to farthest. Bearing is given as a number of clockwise degrees from due north, for example:

  • 0 - due north
  • 180 - due south
  • 90 - due east
  • 270 - due west
  • 230.1 - southwest
  • 359.9 - almost due north

You can convert these numbers to compass point names by using the utility method provided:

Geocoder::Calculations.compass_point(355) # => "N"
Geocoder::Calculations.compass_point(45)  # => "NE"
Geocoder::Calculations.compass_point(208) # => "SW"

Note: when using SQLite distance and bearing values are provided for interface consistency only. They are not very accurate.

To calculate accurate distance and bearing with SQLite or MongoDB:

obj.distance_to([43.9,-98.6])  # distance from obj to point
obj.bearing_to([43.9,-98.6])   # bearing from obj to point
obj.bearing_from(obj2)         # bearing from obj2 to obj

The bearing_from/to methods take a single argument which can be: a [lat,lon] array, a geocoded object, or a geocodable address (string). The distance_from/to methods also take a units argument (:mi, :km, or :nm for nautical miles).

Model Configuration

You are not stuck with using the latitude and longitude database column names (with ActiveRecord) or the coordinates array (Mongo) for storing coordinates. For example:

geocoded_by :address, :latitude  => :lat, :longitude => :lon # ActiveRecord
geocoded_by :address, :coordinates => :coords                # MongoDB

The address method can return any string you'd use to search Google Maps. For example, any of the following are acceptable:

  • "714 Green St, Big Town, MO"
  • "Eiffel Tower, Paris, FR"
  • "Paris, TX, US"

If your model has street, city, state, and country attributes you might do something like this:

geocoded_by :address

def address
  [street, city, state, country].compact.join(', ')
end

For reverse geocoding you can also specify an alternate name attribute where the address will be stored, for example:

reverse_geocoded_by :latitude, :longitude, :address => :location  # ActiveRecord
reverse_geocoded_by :coordinates, :address => :loc                # MongoDB

Advanced Querying

When querying for objects (if you're using ActiveRecord) you can also look within a square rather than a radius (circle) by using the within_bounding_box scope:

distance = 20
center_point = [40.71, 100.23]
box = Geocoder::Calculations.bounding_box(center_point, distance)
Venue.within_bounding_box(box)

This can also dramatically improve query performance, especially when used in conjunction with indexes on the latitude/longitude columns. Note, however, that returned results do not include distance and bearing attributes. If you want to improve performance AND have access to distance and bearing info, use both scopes:

Venue.near(center_point, distance).within_bounding_box(box)

Advanced Geocoding

So far we have looked at shortcuts for assigning geocoding results to object attributes. However, if you need to do something fancy you can skip the auto-assignment by providing a block (takes the object to be geocoded and an array of Geocoder::Result objects) in which you handle the parsed geocoding result any way you like, for example:

reverse_geocoded_by :latitude, :longitude do |obj,results|
  if geo = results.first
    obj.city    = geo.city
    obj.zipcode = geo.postal_code
    obj.country = geo.country_code
  end
end
after_validation :reverse_geocode

Every Geocoder::Result object, result, provides the following data:

  • result.latitude - float
  • result.longitude - float
  • result.coordinates - array of the above two
  • result.address - string
  • result.city - string
  • result.state - string
  • result.state_code - string
  • result.postal_code - string
  • result.country - string
  • result.country_code - string

If you're familiar with the results returned by the geocoding service you're using you can access even more data, but you'll need to be familiar with the particular Geocoder::Result object you're using and the structure of your geocoding service's responses. (See below for links to geocoding service documentation.)

Geocoding Services

By default Geocoder uses Google's geocoding API to fetch coordinates and street addresses (FreeGeoIP is the default for IP address info). However there are several other APIs supported, as well as a variety of settings. Please see the listing and comparison below for details on specific geocoding services (not all settings are supported by all services). Some common configuration options are:

# config/initializers/geocoder.rb
Geocoder.configure(

  # geocoding service (see below for supported options):
  :lookup => :yandex,

  # to use an API key:
  :api_key => "...",

  # geocoding service request timeout, in seconds (default 3):
  :timeout => 5,

  # set default units to kilometers:
  :units => :km,

  # caching (see below for details):
  :cache => Redis.new,
  :cache_prefix => "..."

)

Please see lib/geocoder/configuration.rb for a complete list of configuration options. Additionally, some lookups have their own configuration options, some of which are directly supported by Geocoder. For example, to specify a value for Google's bounds parameter:

# with Google:
Geocoder.search("Paris", :bounds => [[32.1,-95.9], [33.9,-94.3]])

Please see the source code for each lookup to learn about directly supported parameters. Parameters which are not directly supported can be specified using the :params option, by which you can pass arbitrary parameters to any geocoding service. For example, to use Nominatim's countrycodes parameter:

# with Nominatim:
Geocoder.search("Paris", :params => {:countrycodes => "gb,de,fr,es,us"})

Listing and Comparison

The following is a comparison of the supported geocoding APIs. The "Limitations" listed for each are a very brief and incomplete summary of some special limitations beyond basic data source attribution. Please read the official Terms of Service for a service before using it.

Google (:google, :google_premier)

  • API key: required for Premier (do NOT use a key for the free version)
  • Key signup: http://code.google.com/apis/maps/signup.html
  • Quota: 2,500 requests/day, 100,000 with Google Maps API Premier
  • Region: world
  • SSL support: yes
  • Languages: ar, eu, bg, bn, ca, cs, da, de, el, en, en-AU, en-GB, es, eu, fa, fi, fil, fr, gl, gu, hi, hr, hu, id, it, iw, ja, kn, ko, lt, lv, ml, mr, nl, no, pl, pt, pt-BR, pt-PT, ro, ru, sk, sl, sr, sv, tl, ta, te, th, tr, uk, vi, zh-CN, zh-TW (see http://spreadsheets.google.com/pub?key=p9pdwsai2hDMsLkXsoM05KQ&gid=1)
  • Extra options: :bounds - pass SW and NE coordinates as an array of two arrays to bias results towards a viewport
  • Documentation: http://code.google.com/apis/maps/documentation/geocoding/#JSON
  • Terms of Service: http://code.google.com/apis/maps/terms.html#section_10_12
  • Limitations: "You must not use or display the Content without a corresponding Google map, unless you are explicitly permitted to do so in the Maps APIs Documentation, or through written permission from Google." "You must not pre-fetch, cache, or store any Content, except that you may store: (i) limited amounts of Content for the purpose of improving the performance of your Maps API Implementation..."
  • Notes: To use Google Premier set Geocoder.configure(:lookup => :google_premier, :api_key => [key, client, channel]).

Yahoo BOSS (:yahoo)

Yahoo BOSS is not a free service. As of November 17, 2012 Yahoo no longer offers a free geocoding API.

Bing (:bing)

Nominatim (:nominatim)

Yandex (:yandex)

Geocoder.ca (:geocoder_ca)

  • API key: none
  • Quota: ?
  • Region: US and Canada
  • SSL support: no
  • Languages: English
  • Documentation: ?
  • Terms of Service: http://geocoder.ca/?terms=1
  • Limitations: "Under no circumstances can our data be re-distributed or re-sold by anyone to other parties without our written permission."

Mapquest (:mapquest)

  • API key: required for the licensed API, do not use for open tier
  • Quota: ?
  • HTTP Headers: in order to use the licensed API you can configure the http_headers to include a referer as so: Geocoder.configure(:http_headers => { "Referer" => "http://foo.com" }) You can also allow a blank referer from the API management console via mapquest but it is potentially a security risk that someone else could use your API key from another domain.
  • Region: world
  • SSL support: no
  • Languages: English
  • Documentation: http://www.mapquestapi.com/geocoding/
  • Terms of Service: http://info.mapquest.com/terms-of-use/
  • Limitations: ?

Ovi/Nokia (:ovi)

FreeGeoIP (:freegeoip)

  • API key: none
  • Quota: 1000 requests per hour. After reaching the hourly quota, all of your requests will result in HTTP 403 (Forbidden) until it clears up on the next roll over.
  • Region: world
  • SSL support: no
  • Languages: English
  • Documentation: http://github.com/fiorix/freegeoip/blob/master/README.rst
  • Terms of Service: ?
  • Limitations: ?

MaxMind Web Services (:maxmind)

  • API key: required
  • Quota: Request Packs can be purchased
  • Region: world
  • SSL support: yes
  • Languages: English
  • Documentation: http://www.maxmind.com/app/web_services
  • Terms of Service: ?
  • Limitations: ?

Caching

It's a good idea, when relying on any external service, to cache retrieved data. When implemented correctly it improves your app's response time and stability. It's easy to cache geocoding results with Geocoder, just configure a cache store:

Geocoder.configure(:cache => Redis.new)

This example uses Redis, but the cache store can be any object that supports these methods:

  • store#[](key) - retrieves a value
  • store#[]=(key, value) - stores a value
  • store#keys - lists all keys
  • store#del(url) - deletes a value

Even a plain Ruby hash will work, though it's not a great choice (cleared out when app is restarted, not shared between app instances, etc).

You can also set a custom prefix to be used for cache keys:

Geocoder.configure(:cache_prefix => "...")

By default the prefix is geocoder:

If you need to expire cached content:

Geocoder.cache.expire("http://...") # expire cached result for a URL
Geocoder.cache.expire(:all)         # expire all cached results

Do not include the prefix when passing a URL to be expired. Expiring :all will only expire keys with the configured prefix (won't kill every entry in your key/value store).

For an example of a cache store with URL expiry please see examples/autoexpire_cache.rb

Before you implement caching in your app please be sure that doing so does not violate the Terms of Service for your geocoding service.

Forward and Reverse Geocoding in the Same Model

If you apply both forward and reverse geocoding functionality to the same model (say users can supply an address or coordinates and you want to fill in whatever's missing), you will provide two address methods:

  • one for storing the fetched address (reverse geocoding)
  • one for providing an address to use when fetching coordinates (forward geocoding)

For example:

class Venue

  # build an address from street, city, and state attributes
  geocoded_by :address_from_components

  # store the fetched address in the full_address attribute
  reverse_geocoded_by :latitude, :longitude, :address => :full_address
end

However, there can be only one set of latitude/longitude attributes, and whichever you specify last will be used. For example:

class Venue

  geocoded_by :address,
    :latitude  => :fetched_latitude,  # this will be overridden by the below
    :longitude => :fetched_longitude  # same here

  reverse_geocoded_by :latitude, :longitude
end

The reason for this is that we don't want ambiguity when doing distance calculations. We need a single, authoritative source for coordinates!

Once both forward and reverse geocoding has been applied, it is possible to call them sequentially.

For example:

class Venue

  after_validation :geocode, :reverse_geocode

end