README.rdoc

Geocoder¶ ↑

Geocoder adds object geocoding and database-agnostic distance calculations to Ruby on Rails. It’s as simple as calling fetch_coordinates! on your objects, and then using a scope like Venue.near("Billings, MT"). Since it does not rely on proprietary database functions finding geocoded objects in a given area works with out-of-the-box MySQL or even SQLite.

Geocoder is compatible with Rails 2.x and 3.x. This is the README for the 3.x branch. Please see the 2.x branch for installation instructions, documentation, and issues.

1. Install¶ ↑

As a Gem¶ ↑

Add this to your Gemfile:

gem "rails-geocoder", :require => "geocoder"

and run this at the command prompt:

bundle install

Or As a Plugin¶ ↑

At the command prompt:

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

2. Configure¶ ↑

A) Add latitude and longitude columns to your model:

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

B) Tell geocoder where your model stores its address:

geocoded_by :address

C) Optionally, auto-fetch coordinates every time your model is saved:

after_validation :fetch_coordinates

Note that you are not stuck with the latitude and longitude column names, or the address method. See “More On Configuration” below for details.

3. Use¶ ↑

Assuming obj is an instance of a geocoded class, you can get its coordinates:

obj.fetch_coordinates              # fetches and assigns coordinates
obj.fetch_coordinates!             # also saves lat, lon attributes

If you have a lot of objects you can use this Rake task to geocode them all:

rake geocode:all CLASS=YourModel

Once obj is geocoded you can do things like this:

obj.nearbys(30)                    # other objects within 30 miles
obj.distance_to(40.714, -100.234)  # distance to arbitrary point

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

Some utility methods are also available:

# distance (in miles) between Eiffel Tower and Empire State Building
Geocoder::Calculations.distance_between( 48.858205,2.294359,  40.748433,-73.985655 )

# look up coordinates of some location (like searching Google Maps)
Geocoder.fetch_coordinates("25 Main St, Cooperstown, NY")

# find the geographic center (aka center of gravity) of objects or points
Geocoder::Calculations.geographic_center([ city1, city2, city3, [40.22,-73.99], city4 ])

More On Configuration¶ ↑

You are not stuck with using the latitude and longitude database column names for storing coordinates. For example, to use lat and lon:

geocoded_by :address, :latitude  => :lat, :longitude => :lon

The string to use for geocoding can be anything 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 address, city, state, and country attributes you might do something like this:

geocoded_by :location

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

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

Reverse Geocoding¶ ↑