README.md

Geocoder

Geocoder is a complete geocoding solution for Ruby. With Rails it adds geocoding (by street or IP address), reverse geocoding (finding 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").

Please note that this README is for the current HEAD and may document features not present in the latest gem release. For this reason, you may want to instead view the README for your particular version.

Compatibility

• Supports multiple Ruby versions: Ruby 1.9.3, 2.0.x, 2.1.x, JRuby, and Rubinius.
• Supports multiple databases: MySQL, PostgreSQL, SQLite, and MongoDB (1.7.0 and higher).
• Supports Rails 3 and 4. If you need to use it with Rails 2 please see the rails2 branch (no longer maintained, limited feature set).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.

Rails 4.1 Note

Due to a change in ActiveRecord's count method you will need to use count(:all) to explicitly count all columns ("*") when using a near scope. Using near and calling count with no argument will cause exceptions in many cases.

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. Some services — Google notably — enforce a per-second limit in addition to a per-day limit. To avoid exceeding the per-second limit, you can add a SLEEP option to pause between requests for a given amount of time. You can also load objects in batches to save memory, for example:

rake geocode:all CLASS=YourModel SLEEP=0.25 BATCH=100

Avoiding Unnecessary API Requests

Geocoding only needs to be performed under certain conditions. To avoid unnecessary work (and quota usage) you will probably want to geocode an object only when:

• an address is present
• the address has been changed since last save (or it has never been saved)

The exact code will vary depending on the method you use for your geocodable string, but it would be something like this:

after_validation :geocode, if: ->(obj){ obj.address.present? and obj.address_changed? }

Request Geocoding by IP Address

Geocoder adds location and safe_location methods 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

The location method is vulnerable to trivial IP address spoofing via HTTP headers. If that's a problem for your application, use safe_location instead, but be aware that safe_location will not try to trace a request's originating IP through proxy headers; you will instead get the location of the last proxy the request passed through, if any (excepting any proxies you have explicitly whitelisted in your Rack config).

Note that these methods will usually return nil in your test and development environments because things like "localhost" and "0.0.0.0" are not an Internet IP addresses.

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.near([40.71, -100.23], 20, :units => :km)
                                   # venues within 20 kilometres 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