Geocoder¶ ↑

Geocoder is a plugin for Rails that provides database-agnostic object geocoding (via Google) and some utilities for working with geocoded objects. It does not rely on proprietary database functions so reasonably accurate distances can be calculated in MySQL or even SQLite.

Setup¶ ↑

Use the Rails plugin install script:

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

To add geocoding features to a class:

geocoded_by :location

Be sure your class defines attributes for storing latitude and longitude (use float or double database columns) and a location (human-readable address to be geocoded). These attribute names are all configurable; for example, to use address, lat, and lon respectively:

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

A geocodable string is anything you’d use to search Google Maps. 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 your location method might look something like this:

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

Features¶ ↑

Assuming Venue is a geocoded model:

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

Assuming obj has a valid string for its location:

obj.fetch_coordinates                 # returns coordinates [lat, lon]
obj.fetch_coordinates!                # also writes coordinates to object

Assuming obj is geocoded (has latitude and longitude):

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

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")

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

Copyright © 2009 Alex Reisner, released under the MIT license