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Complete Ruby geocoding solution.
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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 named scope like Venue.near("Billings, MT").

Geocoder does not rely on proprietary database functions so finding geocoded objects in a given area is easily done using out-of-the-box MySQL or even SQLite.

1. Install

Install either as a plugin:

script/plugin install git://

or as a gem:

# add to config/environment.rb:
config.gem "rails-geocoder", :lib => "geocoder", :source => ""

# at command prompt:
sudo rake gems:install

2. Configure

A) Get a Google Maps API key (see and store it in a constant:

# eg, in config/initializers/google_maps.rb

B) Add latitude and longitude columns to your model:

script/generate migration AddLatitudeAndLongitudeToYourModel latitude:float longitude:float
rake db:migrate

C) Tell geocoder where your model stores its address:

geocoded_by :address

D) 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 named 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.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.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(', ')

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

To-do List

  • install.rb should do some setup when installed as a plugin

Copyright © 2009 Alex Reisner, released under the MIT license

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