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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 <tt>Venue.near("Billings, MT")</tt>.
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* 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 <tt>rails2</tt> branch (no longer maintained, limited feature set).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 plugin install git://github.com/alexreisner/geocoder.git
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:
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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 <tt>Geocoder::Model::Mongoid</tt> module and then call <tt>geocoded_by</tt>:
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 <i>Latitude/Longitude Order</i> in the <i>Notes on MongoDB</i> section below on how to properly retrieve latitude/longitude coordinates from your objects.
MongoMapper is very similar to Mongoid, just be sure to include <tt>Geocoder::Model::MongoMapper</tt>.
=== Mongo Indices
By default, the methods <tt>geocoded_by</tt> and <tt>reverse_geocoded_by</tt> create a geospatial index. You can avoid index creation with the <tt>:skip_index option</tt>, for example:
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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.
== Request Geocoding by IP Address
Geocoder adds a +location+ method to the standard <tt>Rack::Request</tt> 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.
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
# 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])
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# find the geographic center (aka center of gravity) of objects or points
Geocoder::Calculations.geographic_center([city1, city2, [40.22,-73.99], city4])
Please see the code for more methods and detailed information about arguments (eg, working with kilometers).
When you run a location-aware query the returned objects have two attributes added to them (only w/ ActiveRecord):
* <tt>obj.distance</tt> - number of miles from the search point to this object
* <tt>obj.bearing</tt> - 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:
* <tt>0</tt> - due north
* <tt>180</tt> - due south
* <tt>90</tt> - due east
* <tt>270</tt> - due west
* <tt>230.1</tt> - southwest
* <tt>359.9</tt> - 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"
<i>Note: when using SQLite +distance+ and +bearing+ values are provided for interface consistency only. They are not very accurate.</i>
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 <tt>bearing_from/to</tt> methods take a single argument which can be: a <tt>[lat,lon]</tt> array, a geocoded object, or a geocodable address (string). The <tt>distance_from/to</tt> methods also take a units argument (<tt>:mi</tt> or <tt>:km</tt>).
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:
def address
[street, city, state, country].compact.join(', ')
For reverse geocoding you can also specify an alternate name attribute where the address will be stored, for example:
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reverse_geocoded_by :latitude, :longitude, :address => :location # ActiveRecord
reverse_geocoded_by :coordinates, :address => :loc # MongoDB
== Advanced Querying
When querying for objects (if you're using ActiveRecord) you can also look within a square rather than a radius (circle) by using the <tt>within_bounding_box</tt> scope:
distance = 20
center_point = [40.71, 100.23]
box = Geocoder::Calculations.bounding_box(center_point, distance)
This can also dramatically improve query performance, especially when used in conjunction with indexes on the latitude/longitude columns. Note, however, that returned results do not include +distance+ and +bearing+ attributes. If you want to improve performance AND have access to distance and bearing info, use both scopes:
Venue.near(center_point, distance).within_bounding_box(box)
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 <tt>Geocoder::Result</tt> objects) in which you handle the parsed geocoding result any way you like, for example:
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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
Every <tt>Geocoder::Result</tt> object, +result+, provides the following data:
* <tt>result.latitude</tt> - float
* <tt>result.longitude</tt> - float
* <tt>result.coordinates</tt> - array of the above two
* <tt>result.address</tt> - string
* <tt>result.city</tt> - string
* <tt>result.state</tt> - string
* <tt>result.state_code</tt> - string
* <tt>result.postal_code</tt> - string
* <tt>result.country_code</tt> - 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 <tt>Geocoder::Result</tt> object you're using and the structure of your geocoding service's responses. (See below for links to geocoding service documentation.)
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). Some common configuration options are:
# geocoding service (see below for supported options):
config.lookup = :yahoo
# to use an API key:
config.api_key = "..."
# geocoding service request timeout, in seconds (default 3):
config.timeout = 5
# set default units to kilometers:
config.units = :km
# caching (see below for details):
config.cache = Redis.new
config.cache_prefix = "..."
Please see lib/geocoder/configuration.rb for a complete list of configuration options. Additionally, some lookups have their own configuration options which are listed in the comparison chart below, and as of version 1.2.0 you can pass arbitrary parameters to any geocoding service. For example, to use Nominatim's <tt>countrycodes</tt> parameter:
Geocoder::Configuration.lookup = :nominatim
Geocoder.search("Paris", :params => {:countrycodes => "gb,de,fr,es,us"})
=== 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 (<tt>:google</tt>)
API key:: required for Premier (do NOT use a key for the free version)
Key signup:: http://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 http://spreadsheets.google.com/pub?key=p9pdwsai2hDMsLkXsoM05KQ&gid=1)
Extra options:: <tt>:bounds</tt> - pass SW and NE coordinates as an array of two arrays to bias results towards a viewport
Documentation:: http://code.google.com/apis/maps/documentation/geocoding/#JSON
Terms of Service:: http://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 <tt>Geocoder::Configuration.lookup = :google_premier</tt> and <tt>Geocoder::Configuration.api_key = [key, client, channel]</tt>.
==== Yahoo (<tt>:yahoo</tt>)
API key:: optional in development (required for production apps)
Key signup:: https://developer.apps.yahoo.com/wsregapp
Quota:: 50,000 requests/day, more available by special arrangement
Region:: world
SSL support:: no
Languages:: ?
Documentation:: http://developer.yahoo.com/geo/placefinder/guide/responses.html
Terms of Service:: http://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 (<tt>:bing</tt>)
API key:: required
Key signup:: http://www.bingmapsportal.com
Quota:: 50,000 requests/24 hrs
Region:: world
SSL support:: no
Languages:: ?
Documentation:: http://msdn.microsoft.com/en-us/library/ff701715.aspx
Terms of Service:: http://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 (<tt>:nominatim</tt>)
API key:: none
Quota:: 1 request/second
Region:: world
SSL support:: no
Languages:: ?
Documentation:: http://wiki.openstreetmap.org/wiki/Nominatim
Terms of Service:: http://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 (<tt>:yandex</tt>)
API key:: none
Quota:: 25000 requests / day
Languages:: Russian, Belarusian, Ukrainian, English, Turkish (only for maps of Turkey)
Documentation:: http://api.yandex.com.tr/maps/doc/intro/concepts/intro.xml
Terms of Service:: http://api.yandex.com.tr/maps/doc/intro/concepts/intro.xml#rules
Limitations:: ?
==== Geocoder.ca (<tt>:geocoder_ca</tt>)
API key:: none
Quota:: ?
Region:: US and Canada
SSL support:: no
Languages:: English
Documentation:: ?
Terms of Service:: http://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."
==== Mapquest (<tt>:mapquest</tt>)
API key:: none
Quota:: ?
Region:: world
SSL support:: no
Languages:: English
Documentation:: http://www.mapquestapi.com/geocoding/
Terms of Service:: http://info.mapquest.com/terms-of-use/
Limitations:: ?
Quota:: 1000 requests per hour. After reaching the hourly quota, all of your requests will result in HTTP 403 (Forbidden) until it clears up on the next roll over.
Region:: world
SSL support:: no
Languages:: English
Documentation:: http://github.com/fiorix/freegeoip/blob/master/README.rst
Terms of Service:: ?
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:
* <tt>store#[](key)</tt> - retrieves a value
* <tt>store#[]=(key, value)</tt> - stores a value
* <tt>store#keys</tt> - lists all keys
* <tt>store#del(url)</tt> - deletes a value
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 <tt>geocoder:</tt>
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 <tt>:all</tt> will only expire keys with the configured prefix (won't kill every entry in your key/value store).
For an example of a cache store with URL expiry please see examples/autoexpire_cache.rb
<i>Before you implement caching in your app please be sure that doing so does not violate the Terms of Service for your geocoding service.</i>
== 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!
You can use Geocoder outside of Rails by calling the <tt>Geocoder.search</tt> method:
results = Geocoder.search("McCarren Park, Brooklyn, NY")
This returns an array of <tt>Geocoder::Result</tt> objects with all information provided by the geocoding service. Please see above and in the code for details.
== Testing Apps that Use Geocoder
When writing tests for an app that uses Geocoder it may be useful to avoid network calls and have Geocoder return consistent, configurable results. To do this, configure and use the <tt>:test</tt> lookup. For example:
Geocoder::Configuration.lookup = :test
Geocoder::Lookup::Test.add_stub(
"New York, NY", [
{
'latitude' => 40.7143528,
'longitude' => -74.0059731,
'address' => 'New York, NY, USA',
'state' => 'New York',
'state_code' => 'NY',
'country' => 'United States',
'country_code' => 'US'
}
]
)
Now, any time Geocoder looks up "New York, NY" its results array will contain one result with the above attributes.
== 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 <tt>geocode -h</tt> for details.
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 longitude ([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 (http://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 <tt>to_coordinates</tt> instance method provided by Geocoder. For example:
obj.to_coordinates # => [37.7941013, -122.3951096] # [lat, lon]
Calling <tt>obj.coordinates</tt> 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 <tt>to_coordinates</tt> method instead.
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 <tt>Geocoder::Calculations.distance_between</tt> 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 <tt>Geocoder::Calculations.distance_between</tt>.
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 <tt>rake test</tt>) 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:
http://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 <tt>:always_raise</tt> option:
Geocoder::Configuration.always_raise = [SocketError, TimeoutError]
You can also do this to raise all exceptions:
Geocoder::Configuration.always_raise = :all
See <tt>lib/geocoder/exceptions.rb</tt> for a list of raise-able exceptions.
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 <tt>:select</tt> 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 (c) 2009-12 Alex Reisner, released under the MIT license