Geocoder

Ruby
1

I am trying to write a script that uses the rails-geocoder gem to grab
the latitude and longitude so I can store those values in my own local
table, but am having trouble getting anything to work or to find any
decent documentation describing or even helping me accomplish what I
need done. Does anybody have any suggestions? I have found this example:
http://geocoder.rubyforge.org/ that seems pretty straight forward. I
have a list of cities and states and am just trying to loop through each
and get the lat lon values. Thanks,

-S

2

Shandy N. wrote:

I am trying to write a script that uses the rails-geocoder gem to grab
the latitude and longitude so I can store those values in my own local
table, but am having trouble getting anything to work or to find any
decent documentation describing or even helping me accomplish what I
need done. Does anybody have any suggestions? I have found this example:
http://geocoder.rubyforge.org/ that seems pretty straight forward. I
have a list of cities and states and am just trying to loop through each
and get the lat lon values. Thanks,

-S

I think that geocoder is for full addresses. For just cities, you could
use worldkit. Sending a request like so:
http://brainoff.com/worldkit/geocoder/rest/?city=San+Diego,CA,US

will get you a response like this with the lat & long for the city:
rdf:RDF
geo:Point
geo:long-117.191848</geo:long>
geo:lat32.751575</geo:lat>
</geo:Point>
</rdf:RDF>

You have to make sure there are no spaces in the city field. So cycling
through your list of cities, you’d make sure to concatenate multi word
cities with a ‘+’ before sending the request.

3

My last post wasn’t actually relevant to ruby so here’s a little snippet
using ruby, sqlite and worldkit. I’m just learning ruby myself so this
might not be the best way to do this.

require ‘open-uri’
require ‘sqlite3’

make a table with two records, Dallas, TX and Lansing, MI

database = SQLite3::Database.new( “cities.database” )
database.execute( “create table city_names (id INTEGER PRIMARY KEY, name
TEXT, state TEXT, country TEXT, latitude NUMERIC, long NUMERIC);”)
database.execute( “insert into city_names (name, state, country) values
(‘Dallas’, ‘TX’, ‘US’)”)
database.execute( “insert into city_names (name, state, country) values
(‘Lansing’, ‘MI’, ‘US’)”)

class Geocoder
def initialize(db)
@db = db
@rows = db.execute( “select * from city_names”)
end

def update_coords
@link = “”
@rows.each do |item|
@link = “#{item[1]},#{item[2]},#{item[3]}”
open(“http://brainoff.com/worldkit/geocoder/rest/?city=#{@link}”)
do |f|
sd = f.read
@long = sd.scan(/long>(.)</)
@lat = sd.scan(/lat>(.)</)
end
@db.execute( “UPDATE city_names SET long =‘#{@long[0][0]}’ WHERE
id=#{item[0]}”)
@db.execute( “UPDATE city_names SET latitude =‘#{@lat[0][0]}’ WHERE
id=#{item[0]}”)
end
end
end

geo = Geocoder.new(database)
geo.update_coords

4

Hi, here is an ActiveRecord based solution gist:338506 · GitHub
It
is based on Peter S.'s solution. It also populates most of the 50
cities
found at Profiles of the 50 Largest Cities of the United States

Here is the same thing, but using the geocoder gem that Shandy asked
about

I also added some use cases for it that work with the data it populates
into
the db, such as
dallas.distance_to austin
texas_cities = City.find_all_by_state(‘TX’).map { |city| city.lat_lon }
Geocoder.geographic_center texas_cities
near_sacramento = City.find_by_name(‘Sacramento’).nearbys(100)

You can see the gem homepage at GitHub - alexreisner/geocoder: Complete Ruby geocoding solution.
Wasn’t very straightforward how to use this outside of Rails, but I
eventually got it. (had to do a little code digging to understand the
errors
and query some mailing lists to find solutions)
$ gem install rails-geocoder

Then get a google api key at

The license says your application must be available to the public, free
or
charge, otherwise you should be using

They want you to list a site your app will be available through. I gave
them
the URL of the gist the example is hosted at :)~

Anyway, a very simple program that correctly uses the gem to get
results:
require ‘net/http’
require ‘rubygems’
require ‘active_record’
require ‘geocoder’

Geocoder::GOOGLE_MAPS_API_KEY = ‘your key goes here’
p Geocoder.fetch_coordinates(“Wichita,KS,US”)