Geocoding

About eighteen months ago I compiled a series of reviews of Ruby on Rails plugins concerned with geography. I put together a comparison chart and posted it on this blog. It subsequently found a new home on a wiki, but lately that wiki has rarely been accessible so I decided it was time to move it all back into this site. You can now find the comparison chart at: /process/resources/rails-geo-plugins/ A few updates have been lost along the way as they were solely made on the wiki, but hopefully it’s still of use. Since I published the original reviews and chart my attention has wandered a little from the geo plugin scene, so please do flag up any new plugins, changes in features or fixes that I may have missed. I’m going to be trying to check through all the existing listings to update them but that may take a while, so comments here may well encourage me to focus more quickly. ...

GeoX is the latest kid on the Ruby on Rails geocoding block. The plugin was announced a couple of weeks ago and I’ve been meaning to explore it ever since, just in case it had any new features and also so that I can add it to my comparison chart. The feature set of GeoX is fairly straightforward. It supports a number of geocoding back ends: obviously google and yahoo are covered, but also mapquest’s relatively recent API. The standard lookup process is much like that provided by several other plugins—the sample given is: ...

There’s quite a bit of overlap between GeoKit and acts_as_geocodable/graticule, as the latter pair were based on GeoKit. But it provides at least one feature (IP-based location lookup) that they don’t, so I decided to give it a whirl. Since my main geographically related projects are both now based on plugins that I’m pretty happy with and which suit them well, I decided to resuscitate an old sample piece. A few months back I wrote about scraping the Grand Rapids bus routes site and put up a toy application utilising the resource features in then-edge Rails. I’ve been meaning to return to that project to test out some features in ActiveResource, but in the meantime it seemed like it might be useful to be able to search for the nearest bus stop. ...

After writing my review of acts_as_geocodable/graticule earlier in the week, I decided to go searching for geocoding services that might offer data for addresses outside of North America. One that I came across is at Local Search Maps. There’s an introductory blog entry here. The API is a little different in that it returns its data as javascript strings, but otherwise it’s simple enough to send a GET for a given address and get back the data. To see how easy it is, I decided to code up an extra geocoder for graticule that would use this service. ...

acts_as_geocodable ( blog entry, repository) is the newest kid on the rails geo plugin block. It actually consists of two parts, a gem called graticule which handles the actual geocoding, interacting with external services, etc, and the plugin which offers extensions to your models. I like that separation. Having the generalised code in a gem and the rails-specific hooks in a plugin makes a lot of sense and makes it much easier to use the core code in non-rails ruby apps, and having a single gem that supports multiple services allows for built-in failover should the preferred geocoder be unavailable. ...

Wednesday’s post on acts_as_locateable didn’t do much to explain what the patch to the plugin’s methods was doing to allow us to pass extra arguments to ActiveRecord#find. The secret is in the *, or array argument. A normal method will have a fixed number of arguments: def simple_method(first, second, third) puts "#{first} : #{second} : #{third}" end simple_method('one', 'two', 'three') >> one : two : three and sometimes we can develop that by allowing default values for those arguments: ...

There have been quite a few geographically-themed Rails plugins emerging over the past few months and I decided it was time to try out acts_as_locateable. Acts_as_locateable is based on ZipCodeSearch. It loads in a database mapping US zip codes to coordinates and then adds convenience methods to ActiveRecord objects that let you search by distance. eg. Event.find_within_radius(50, '49503') will return all events within 50 miles of me. What the standard plugin doesn’t allow is the passing in of more search parameters. So if I wanted to limit that search to future events I’d have to retrieve all the results and iterate over them. In a large system that could be very inefficient. ...