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## FEATURE SUMMARY This plugin provides key functionality for location-oriented Rails applications: - Distance calculations, for both flat and spherical environments. For example, given the location of two points on the earth, you can calculate the miles/KM between them. - ActiveRecord distance-based finders. For example, you can find all the points in your database within a 50-mile radius. - Geocoding from multiple providers. It currently supports Google, Yahoo, Geocoder.us, and Geocoder.ca geocoders, and it provides a uniform response structure from all of them. It also provides a fail-over mechanism, in case your input fails to geocode in one service. - IP-based location lookup utilizing hostip.info. Provide an IP address, and get city name and latitude/longitude in return - A before_filter helper to geocoder the user's location based on IP address, and retain the location in a cookie. The goal of this plugin is to provide the common functionality for location-oriented applications (geocoding, location lookup, distance calculation) in an easy-to-use package. ## A NOTE ON TERMINOLOGY Throughout the code and API of this, latitude and longitude are referred to as lat and lng. We've found over the long term the abbreviation saves lots of typing time. ## DISTANCE CALCULATIONS AND QUERIES If you want only distance calculation services, you need only mix in the Mappable module like so: class Location include GeoKit::Mappable end After doing so, you can do things like: Location.distance_between(from, to) with optional parameters :units and :formula. Values for :units can be :miles or :kms with :miles as the default. Values for :formula can be :sphere or :flat with :sphere as the default. :sphere gives you Haversine calculations, while :flat gives the Pythagoreum Theory. These defaults persist through out the plug-in. You can also do: location.distance_to(other) The real power and utility of the plug-in is in its query support. This is achieved through mixing into an ActiveRecord model object. Doing so, looks as below: class Location < ActiveRecord::Base acts_as_mappable end The plug-in uses the above-mentioned defaults, but can be modified to use different units and a different formula. This is done through the :default_units and :default_formula keys which accept the same values as mentioned above. The plug-in creates a calculated column and potentially a calculated condition. By default, these are known as "distance" but this can be changed through the :distance_field_name key. So, an alternative invocation would look as below: class Location < ActiveRecord::Base acts_as_mappable :default_units => :kms, :default_formula => :flat, :distance_field_name => :distance end You can also define alternative column names for latitude and longitude using the :lat_column_name and :lng_column_name keys. The defaults are 'lat' and 'lng' respectively. Thereafter, a set of finder methods are made available. Below are the different combinations: Origin as a two-element array of latititude/longitude: find(:all, :origin => [37.792,-122.393]) Origin as a geocodeable string: find(:all, :origin => '100 Spear st, San Francisco, CA') Origin as an object which responds to lat and lng methods, or latitude and longitude methods, or whatever methods you have specified for lng_column_name and lat_column_name: find(:all, :origin=>my_store) # my_store.lat and my_store.lng methods exist In addition to adding a distance column, substitutes the distance formula for the distance field in the conditions clause. This saves from having to add complicated SQL in the conditions clause. The result set returns model instances that are less than 5 units away. find(:all, :origin => @somewhere, :conditions => "distance < 5") NOTE: conditions can also be compound as in :conditions => "distance < 100 and state ='TX'". If :origin is not provided in the finder call, the find method works as normal. Further, the key is removed from the :options hash prior to invoking the superclass behavior. Other convenience methods work intuitively and are as follows: find_within(distance, :origin => @somewhere) find_beyond(distance, :origin => @somewhere) find_closest(:origin => @somewhere) find_farthest(:origin => @somewhere) where the options respect the defaults, but can be overridden if desired. Lastly, if all that is desired is the raw SQL for distance calculations, you can use the following: distance_sql(origin, units=default_units, formula=default_formula) Thereafter, you are free to use it in find_by_sql as you wish. There are methods available to enable you to get the count based upon the find condition that you have provided. These all work similarly to the finders. So for instance: count(:origin, :conditions => "distance < 5") count_within(distance, :origin => @somewhere) count_beyond(distance, :origin => @somewhere) ## IP GEOCODING You can obtain the location for an IP at any time using the geocoder as in the following example: location = IpGeocoder.geocode('18.104.22.168') where Location is a GeoLoc instance containing the latitude, longitude, city, state, and country code. Also, the success value is true. If the IP cannot be geocoded, a GeoLoc instance is returned with a success value of false. It should be noted that the IP address needs to be visible to the Rails application. In other words, you need to ensure that the requesting IP address is forwarded by any front-end servers that are out in front of the Rails app. Otherwise, the IP will always be that of the front-end server. ## IP GEOCODING HELPER A class method called geocode_ip_address has been mixed into the ActionController::Base. This enables before_filter style lookup of the IP address. Since it is a filter, it can accept any of the available filter options. Usage is as below: class LocationAwareController < ActionController::Base geocode_ip_address end A first-time lookup will result in the GeoLoc class being stored in the session as :geo_location as well as in a cookie called :geo_session. Subsequent lookups will use the session value if it exists or the cookie value if it doesn't exist. The last resort is to make a call to the web service. Clients are free to manage the cookie as they wish. The intent of this feature is to be able to provide a good guess as to a new visitor's location. ## INTEGRATED FIND AND GEOCODING Geocoding has been integrated with the finders enabling you to pass a physical address or an IP address. This would look the following: Location.find_farthest(:origin => '22.214.171.124') Location.find_farthest(:origin => 'Irving, TX') where the IP or physical address would be geocoded to a location and then the resulting latitude and longitude coordinates would be used in the find. This is not expected to be common usage, but it can be done nevertheless. ## ADDRESS GEOCODING GeoKit can geocode addresses using multiple geocodeing web services. Currently, GeoKit supports Google, Yahoo, and Geocoder.us geocoding services. These geocoder services are made available through three classes: GoogleGeocoder, YahooGeocoder, and UsGeocoder. Further, an additional geocoder class called MultiGeocoder incorporates an ordered failover sequence to increase the probability of successful geocoding. All classes are called using the following signature: include GeoKit::Geocoders location = XxxGeocoder.geocode(address) where you replace Xxx Geocoder with the appropriate class. A GeoLoc instance is the result of the call. This class has a "success" attribute which will be true if a successful geocoding occurred. If successful, the lat and lng properties will be populated. Geocoders are named with the naming convention NameGeocoder. This naming convention enables Geocoder to auto-detect its sub-classes in order to create methods called name_geocoder(address) so that all geocoders are called through the base class. This is done purely for convenience; the individual geocoder classes are expected to be used independently. The MultiGeocoder class requires the configuration of a provider order which dictates what order to use the various geocoders. Ordering is done through the PROVIDER_ORDER constant found in environment.rb. On installation, this plugin appends a template for your API keys to your environment.rb. Make sure your failover configuration matches the usage characteristics of your application -- for example, if you routinely get bogus input to geocode, your code will be much slower if you have to failover among multiple geocoders before determining that the input was in fact bogus. The Geocoder.geocode method returns a GeoLoc object. Basic usage: loc=Geocoder.geocode('100 Spear St, San Francisco, CA') if loc.success puts loc.lat puts loc.lng puts loc.full_address end ## INTEGRATED FIND WITH ADDRESS GEOCODING Just has you can pass an IP address directly into an ActiveRecord finder as the origin, you can also pass a physical address as the origin: Location.find_closest(:origin => '100 Spear st, San Francisco, CA') where the physical address would be geocoded to a location and then the resulting latitude and longitude coordinates would be used in the find. Note that if the address fails to geocode, the find method will raise an ActiveRecord::GeocodeError you must be prepared to catch. Alternatively, You can geocoder the address beforehand, and pass the resulting lat/lng into the finder if successful. HOW TO . . . ================================================================================= ## How to install the GeoKit plugin cd [APP_ROOT] ruby script/plugin install svn://rubyforge.org/var/svn/geokit/trunk or, to install as an external (your project must be version controlled): ruby script/plugin install -x svn://rubyforge.org/var/svn/geokit/trunk ## How to find all stores within a 10-mile radius of a given lat/lng 1. ensure your stores table has lat and lng columns with numeric or float datatypes to store your latitude/longitude 3. use acts_as_mappable on your store model: class Store < ActiveRecord::Base acts_as_mappable ... end 3. finders now have extra capabilities: Store.find(:all, :origin =>[32.951613,-96.958444], :conditions=>'distance<10') ## How to geocode an address 1. configure your geocoder key(s) in environment.rb 2. also in environment.rb, make sure that PROVIDER_ORDER reflects the geocoder(s). If you only want to use one geocoder, there should be only one symbol in the array. For example: PROVIDER_ORDER=[:google] 3. Test it out in script/console include GeoKit::Geocoders res = MultiGeocoder.geocode('100 Spear St, San Francisco, CA') puts res.lat puts res.lng puts res.full_address ... etc. The return type is GeoLoc, see the API for all the methods you can call on it. ## How to find all stores within 10 miles of a given address 1. as above, ensure your table has the lat/lng columns, and you've applied acts_as_mappable to the Store model. 2. configure and test out your geocoder, as above 3. pass the address in under the :origin key Store.find(:all, :origin=>'100 Spear st, San Francisco, CA', :conditions=>'distance<10') 4. you can also use a zipcode, or anything else that's geocodable: Store.find(:all, :origin=>'94117', :conditions=>'distance<10') ## How to sort a query by distance from an origin You now have access to a 'distance' column, and you can use it as you would any other column. For example: Store.find(:all, :origin=>'94117', :order=>'distance') HIGH-LEVEL NOTES ON WHAT'S WHERE ================================================================================= acts_as_mappable.rb, as you'd expect, contains the ActsAsMappable module which gets mixed into your models to provide the location-based finder goodness. mappable.rb contains the Mappable module, which provides basic distance calculation methods, i.e., calculating the distance between two points. mappable.rb also contains LatLng and GeoLoc. LatLng is a simple container for latitude and longitude, but it's made more powerful by mixing in the above-mentioned Mappable module -- therefore, you can calculate easily the distance between two LatLng ojbects with distance = first.distance_to(other) GeoLoc (also in mappable.rb) represents an address or location which has been geocoded. You can get the city, zipcode, street address, etc. from a GeoLoc object. GeoLoc extends LatLng, so you also get lat/lng AND the Mappable modeule goodness for free. geocoders.rb contains the geocoder classes. ip_geocode_lookup.rb contains the before_filter helper method which enables auto lookup of the requesting IP address. ## IMPORTANT NOTE: We have appended to your environment.rb file Installation of this plugin has appended an API key template to your environment.rb file. You *must* add your own keys for the various geocoding services if you want to use geocoding. If you need to refer to the original template again, see the api_keys_template file in the root of the plugin.