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, and JRuby.

• Supports multiple databases: MySQL, PostgreSQL, SQLite, and MongoDB (1.7.0 and higher).

• Supports Rails 3. If you need to use it with Rails 2 please see the rails2 branch (no longer maintained, limited feature set).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.

Install¶ ↑

As a Gem¶ ↑

Add to your Gemfile:

gem "geocoder"

and run at the command prompt:

bundle install

Or As a Plugin¶ ↑

At the command prompt:

rails plugin install git://github.com/alexreisner/geocoder.git

Configure Object Geocoding¶ ↑

In the below, note that addresses may be street or IP addresses.

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 “More on 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

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.

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:

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

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 or :km).

More on 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 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 used 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). The configuration options are:

# config/initializers/geocoder.rb

# geocoding service (see below for supported options):
Geocoder::Configuration.lookup = :yahoo

# to use an API key:
Geocoder::Configuration.api_key = "..."

# geocoding service request timeout, in seconds (default 3):
Geocoder::Configuration.timeout = 5

# use HTTPS for geocoding service connections:
Geocoder::Configuration.use_https = true

# language to use (for search queries and reverse geocoding):
Geocoder::Configuration.language = :de

# use a proxy to access the service:
Geocoder::Configuration.http_proxy  = "127.4.4.1"
Geocoder::Configuration.https_proxy = "127.4.4.2" # only if HTTPS is needed

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

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)¶ ↑

API key

optional (required for Premier)

Key signup

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 spreadsheets.google.com/pub?key=p9pdwsai2hDMsLkXsoM05KQ&gid=1)

Documentation

code.google.com/apis/maps/documentation/geocoding/#JSON

Terms of Service

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::Configuration.lookup = :google_premier and Geocoder::Configuration.api_key = [key, client, channel].

Yahoo (:yahoo)¶ ↑

API key

optional in development (required for production apps)

Key signup

developer.apps.yahoo.com/wsregapp

Quota

50,000 requests/day, more available by special arrangement

Region

world

SSL support

no

Languages

?

Documentation

developer.yahoo.com/geo/placefinder/guide/responses.html

Terms of Service

info.yahoo.com/legal/us/yahoo/maps/mapsapi/mapsapi-2141.html

Limitations

“YOU SHALL NOT… (viii) store or allow end users to store map imagery, map data or geocoded location information from the Yahoo! Maps APIs for any future use; (ix) use the stand-alone geocoder for any use other than displaying Yahoo! Maps or displaying points on Yahoo! Maps;”

Bing (:bing)¶ ↑

API key

required

Key signup

www.bingmapsportal.com

Quota

50,000 requests/24 hrs

Region

world

SSL support

no

Languages

?

Documentation

msdn.microsoft.com/en-us/library/ff701715.aspx

Terms of Service

www.microsoft.com/maps/product/terms.html

Limitations

No country codes or state names. Must be used on “public-facing, non-password protected web sites,” “in conjunction with Bing Maps or an application that integrates Bing Maps.”

Nominatim (:nominatim)¶ ↑

API key

none

Quota

1 request/second

Region

world

SSL support

no

Languages

?

Documentation

wiki.openstreetmap.org/wiki/Nominatim

Terms of Service

wiki.openstreetmap.org/wiki/Nominatim_usage_policy

Limitations

Please limit request rate to 1 per second and include your contact information in User-Agent headers. Data licensed under CC-BY-SA (you must provide attribution).

Yandex (:yandex)¶ ↑

API key

required

Key signup

api.yandex.ru/maps/intro/concepts/intro.xml#apikey

Quota

?

Region

Russia

SSL support

no

Languages

Russian, Belarusian, and Ukrainian

Documentation

api.yandex.ru/maps/geocoder/doc/desc/concepts/response_structure.xml

Terms of Service

api.yandex.com/direct/eula.xml?ncrnd=8453

Limitations

?

Geocoder.ca (:geocoder_ca)¶ ↑

API key

none

Quota

?

Region

US and Canada

SSL support

no

Languages

English

Documentation

?

Terms of Service

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.”

FreeGeoIP¶ ↑

API key

none

Quota

?

Region

world

SSL support

no

Languages

English

Documentation

github.com/fiorix/freegeoip/blob/master/README.rst

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::Configuration.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

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::Configuration.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).

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!

Use Outside of Rails¶ ↑

You can use Geocoder outside of Rails by calling the Geocoder.search method:

results = Geocoder.search("McCarren Park, Brooklyn, NY")

This returns an array of Geocoder::Result objects with all information provided by the geocoding service. Please see above and in the code for details.

Command Line Interface¶ ↑

When you install the Geocoder gem it adds a geocode command to your shell. You can search for a street address, IP address, postal code, coordinates, etc just like you can with the Geocoder.search method for example:

$ geocode 29.951,-90.081
Latitude:         29.952211
Longitude:        -90.080563
Full address:     1500 Sugar Bowl Dr, New Orleans, LA 70112, USA
City:             New Orleans
State/province:   Louisiana
Postal code:      70112
Country:          United States
Google map:       http://maps.google.com/maps?q=29.952211,-90.080563

There are also a number of options for setting the geocoding API, key, and language, viewing the raw JSON reponse, and more. Please run geocode -h for details.

Notes on MongoDB¶ ↑

The Near Method¶ ↑

Mongo document classes (Mongoid and MongoMapper) have a built-in near scope, but since it only works two-dimensions Geocoder overrides it with its own spherical near method in geocoded classes.

Latitude/Longitude Order¶ ↑

Coordinates are generally printed and spoken as latitude, then logitude ([lat,lon]). Geocoder respects this convention and always expects method arguments to be given in [lat,lon] order. However, MongoDB requires that coordinates be stored in [lon,lat] order as per the GeoJSON spec (geojson.org/geojson-spec.html#positions), so internally they are stored “backwards.” However, this does not affect order of arguments to methods when using Mongoid or MongoMapper.

To access an object’s coordinates in the conventional order, use the to_coordinates instance method provided by Geocoder. For example:

obj.to_coordinates  # => [37.7941013, -122.3951096] # [lat, lon]

Calling obj.coordinates directly returns the internal representation of the coordinates which, in the case of MongoDB, is probably the reverse of what you want:

obj.coordinates     # => [-122.3951096, 37.7941013] # [lon, lat]

For consistency with the rest of Geocoder, always use the to_coordinates method instead.

Distance Queries in SQLite¶ ↑

SQLite’s lack of trigonometric functions requires an alternate implementation of the near scope. When using SQLite, Geocoder will automatically use a less accurate algorithm for finding objects near a given point. Results of this algorithm should not be trusted too much as it will return objects that are outside the given radius, along with inaccurate distance and bearing calculations.

Discussion¶ ↑

There are few options for finding objects near a given point in SQLite without installing extensions:

1. Use a square instead of a circle for finding nearby points. For example, if you want to find points near 40.71, 100.23, search for objects with latitude between 39.71 and 41.71 and longitude between 99.23 and 101.23. One degree of latitude or longitude is at most 69 miles so divide your radius (in miles) by 69.0 to get the amount to add and subtract from your center coordinates to get the upper and lower bounds. The results will not be very accurate (you’ll get points outside the desired radius), but you will get all the points within the required radius.

2. Load all objects into memory and compute distances between them using the Geocoder::Calculations.distance_between method. This will produce accurate results but will be very slow (and use a lot of memory) if you have a lot of objects in your database.

3. If you have a large number of objects (so you can’t use approach #2) and you need accurate results (better than approach #1 will give), you can use a combination of the two. Get all the objects within a square around your center point, and then eliminate the ones that are too far away using Geocoder::Calculations.distance_between.

Because Geocoder needs to provide this functionality as a scope, we must go with option #1, but feel free to implement #2 or #3 if you need more accuracy.

Tests¶ ↑

Geocoder comes with a test suite (just run rake test) that mocks ActiveRecord and is focused on testing the aspects of Geocoder that do not involve executing database queries. Geocoder uses many database engine-specific queries which must be tested against all supported databases (SQLite, MySQL, etc). Ideally this involves creating a full, working Rails application, and that seems beyond the scope of the included test suite. As such, I have created a separate repository which includes a full-blown Rails application and some utilities for easily running tests against multiple environments:

github.com/alexreisner/geocoder_test

Error Handling¶ ↑

By default Geocoder will rescue any exceptions raised by calls to the geocoding service and return an empty array (using warn() to inform you of the error). You can override this and implement custom error handling for certain exceptions by using the :always_raise option:

Geocoder::Configuration.always_raise = [SocketError, TimeoutError]

Known Issue¶ ↑

You cannot use the near scope with another scope that provides an includes option because the SELECT clause generated by near will overwrite it (or vice versa). Instead, try using joins and pass a :select option to the near scope to get the columns you want. For example:

# instead of City.near(...).includes(:venues)
City.near("Omaha, NE", 20, :select => "cities.*, venues.*").joins(:venues)

If anyone has a more elegant solution to this problem I am very interested in seeing it.

Copyright © 2009-11 Alex Reisner, released under the MIT license