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Commit b956f0c5 authored by Alex Reisner's avatar Alex Reisner
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Add options for setting custom latitude and longitude attributes.

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README.rdoc
+ 28
− 9
View file @ b956f0c5
......@@ -12,9 +12,17 @@ To add geocoding features to a class:
geocoded_by :location
Be sure your class defines read/write attributes +latitude+ and +longitude+ as well as a method called +location+ (or whatever name you pass to +geocoded_by+) that returns a string suitable for passing to a Google Maps search, for example:
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:
geocoded_by :address,
:latitude => :lat,
:longitude => :lon
A geocodable string is basically 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:
......@@ -23,21 +31,32 @@ If your model has +address+, +city+, +state+, and +country+ attributes your +loc
end
== Examples
== Features
Assuming +Venue+ is a geocoded model:
Look up coordinates of an object:
Venue.find_near('Omaha, NE, US', 20) # venues within 20 miles of Omaha
Venue.geocoded # venues with coordinates
Venue.not_geocoded # venues without coordinates
obj.fetch_coordinates # returns an array [lat, lon]
obj.fetch_and_assign_coordinates # writes values to +latitude+ and +longitude+
Assuming +obj+ has a valid string for its +location+:
obj.fetch_coordinates # returns coordinates [lat, lon]
obj.fetch_and_assign_coordinates # writes values to object
Find distance between object and a point:
obj.distance_to(40.71432, -100.23487) # in miles
obj.distance_to(40.71432, -100.23487, :km) # in kilometers
obj.distance_to(40.71432, -100.23487) # in miles
obj.distance_to(40.71432, -100.23487, :km) # in kilometers
Some utility methods are also available:
Find objects within 20 miles of a point:
# 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")
Venue.find_near('Omaha, NE, US', 20) # Venue is a geocoded model
Please see the code for more methods and detailed information about arguments.
......
init.rb
+ 4
− 2
View file @ b956f0c5
......@@ -4,8 +4,10 @@ ActiveRecord::Base.class_eval do
# Include the Geocoder module and set the method name which returns
# the geo-search string.
#
def self.geocoded_by(method_name = :location)
def self.geocoded_by(method_name = :location, options = {})
include Geocoder
@geocoder_method_name = method_name
@geocoder_method_name = method_name
@geocoder_latitude_attr = options[:latitude] || :latitude
@geocoder_longitude_attr = options[:longitude] || :longitude
end
end
lib/geocoder.rb
+ 97
− 81
View file @ b956f0c5
......@@ -20,25 +20,6 @@ module Geocoder
end
end
##
# Query Google for the coordinates of the given phrase.
# Returns array [lat,lon] if found, nil if not found or if network error.
#
def self.fetch_coordinates(query)
return nil unless doc = self.search(query)
# Make sure search found a result.
e = doc.elements['kml/Response/Status/code']
return nil unless (e and e.text == "200")
# Isolate the relevant part of the result.
place = doc.elements['kml/Response/Placemark']
# If there are multiple results, blindly use the first.
coords = place.elements['Point/coordinates'].text
coords.split(',')[0...2].reverse.map{ |i| i.to_f }
end
##
# Methods which will be class methods of the including class.
#
......@@ -53,14 +34,81 @@ module Geocoder
latitude, longitude = location.is_a?(Array) ?
location : Geocoder.fetch_coordinates(location)
return [] unless (latitude and longitude)
all(Geocoder.find_near_options(latitude, longitude, radius, options))
all(find_near_options(latitude, longitude, radius, options))
end
##
# Get the name of the method that returns the search string.
# Get options hash suitable for passing to ActiveRecord.find to get
# records within a radius (in miles) of the given point.
# Taken from excellent tutorial at:
# http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL
#
# Options hash may include:
#
# +order+ :: column(s) for ORDER BY SQL clause
# +limit+ :: number of records to return (for LIMIT SQL clause)
# +offset+ :: number of records to skip (for LIMIT SQL clause)
#
def find_near_options(latitude, longitude, radius = 20, options = {})
# Set defaults/clean up arguments.
options[:order] ||= 'distance ASC'
radius = radius.to_i
# Constrain search to a (radius x radius) square.
factor = (Math::cos(latitude * Math::PI / 180.0) * 69.0).abs
lon_lo = longitude - (radius / factor);
lon_hi = longitude + (radius / factor);
lat_lo = latitude - (radius / 69.0);
lat_hi = latitude + (radius / 69.0);
# Build limit clause.
limit = nil
if options[:limit] or options[:offset]
options[:offset] ||= 0
limit = "#{options[:offset]},#{options[:limit]}"
end
# Generate hash.
{
:select => "*, 3956 * 2 * ASIN(SQRT(" +
"POWER(SIN((#{latitude} - #{geocoder_latitude_attr}) * " +
"PI() / 180 / 2), 2) + COS(#{latitude} * PI()/180) * " +
"COS(#{geocoder_latitude_attr} * PI() / 180) * " +
"POWER(SIN((#{longitude} - #{geocoder_longitude_attr}) * " +
"PI() / 180 / 2), 2) )) as distance",
:conditions => [
"#{geocoder_latitude_attr} BETWEEN ? AND ? AND " +
"#{geocoder_longitude_attr} BETWEEN ? AND ?",
lat_lo, lat_hi, lon_lo, lon_hi],
:having => "distance <= #{radius}",
:order => options[:order],
:limit => limit
}
end
##
# Name of the method that returns the search string.
#
def geocoder_method_name
defined?(@geocoder_method_name) ? @geocoder_method_name : :location
defined?(@geocoder_method_name) ?
@geocoder_method_name : :location
end
##
# Name of the latitude attribute.
#
def geocoder_latitude_attr
defined?(@geocoder_latitude_attr) ?
@geocoder_latitude_attr : :latitude
end
##
# Name of the longitude attribute.
#
def geocoder_longitude_attr
defined?(@geocoder_longitude_attr) ?
@geocoder_longitude_attr : :longitude
end
end
......@@ -69,15 +117,18 @@ module Geocoder
# are defined in <tt>distance_between</tt> class method.
#
def distance_to(lat, lon, units = :mi)
Geocoder.distance_between(latitude, longitude, lat, lon, :units => units)
mylat = read_attribute(self.class.geocoder_latitude_attr)
mylon = read_attribute(self.class.geocoder_longitude_attr)
Geocoder.distance_between(mylat, mylon, lat, lon, :units => units)
end
##
# Fetch coordinates based on the object's object's +location+. Returns an
# Fetch coordinates based on the object's location. Returns an
# array <tt>[lat,lon]</tt>.
#
def fetch_coordinates
Geocoder.fetch_coordinates(send(self.class.geocoder_method_name))
location = read_attribute(self.class.geocoder_method_name)
Geocoder.fetch_coordinates(location)
end
##
......@@ -86,12 +137,31 @@ module Geocoder
def fetch_and_assign_coordinates
returning fetch_coordinates do |c|
unless c.blank?
self.latitude = c[0]
self.longitude = c[1]
write_attribute(self.class.geocoder_latitude_attr, c[0])
write_attribute(self.class.geocoder_longitude_attr, c[1])
end
end
end
##
# Query Google for the coordinates of the given phrase.
# Returns array [lat,lon] if found, nil if not found or if network error.
#
def self.fetch_coordinates(query)
return nil unless doc = self.search(query)
# Make sure search found a result.
e = doc.elements['kml/Response/Status/code']
return nil unless (e and e.text == "200")
# Isolate the relevant part of the result.
place = doc.elements['kml/Response/Placemark']
# If there are multiple results, blindly use the first.
coords = place.elements['Point/coordinates'].text
coords.split(',')[0...2].reverse.map{ |i| i.to_f }
end
##
# Calculate the distance between two points on Earth (Haversine formula).
# Takes two sets of coordinates and an options hash:
......@@ -126,60 +196,6 @@ module Geocoder
degrees * (Math::PI / 180)
end
##
# Get options hash suitable for passing to ActiveRecord.find to get
# records within a radius (in miles) of the given point.
# Taken from excellent tutorial at:
# http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL
#
# Options hash may include:
#
# +latitude+ :: name of column storing latitude data
# +longitude+ :: name of column storing longitude data
# +order+ :: column(s) for ORDER BY SQL clause
# +limit+ :: number of records to return (for LIMIT SQL clause)
# +offset+ :: number of records to skip (for LIMIT SQL clause)
#
def self.find_near_options(latitude, longitude, radius = 20, options = {})
# Set defaults/clean up arguments.
options[:latitude] ||= 'latitude'
options[:longitude] ||= 'longitude'
options[:order] ||= 'distance ASC'
radius = radius.to_i
# Constrain search to a (radius x radius) square.
factor = (Math::cos(latitude * Math::PI / 180.0) * 69.0).abs
lon_lo = longitude - (radius / factor);
lon_hi = longitude + (radius / factor);
lat_lo = latitude - (radius / 69.0);
lat_hi = latitude + (radius / 69.0);
# Build limit clause.
limit = nil
if options[:limit] or options[:offset]
options[:offset] ||= 0
limit = "#{options[:offset]},#{options[:limit]}"
end
# Generate hash.
{
:select => "*, 3956 * 2 * ASIN(SQRT(" +
"POWER(SIN((#{latitude} - #{options[:latitude]}) * " +
"PI() / 180 / 2), 2) + COS(#{latitude} * PI()/180) * " +
"COS(#{options[:latitude]} * PI() / 180) * " +
"POWER(SIN((#{longitude} - #{options[:longitude]}) * " +
"PI() / 180 / 2), 2) )) as distance",
:conditions => [
"#{options[:latitude]} BETWEEN ? AND ? AND " +
"#{options[:longitude]} BETWEEN ? AND ?",
lat_lo, lat_hi, lon_lo, lon_hi],
:having => "distance <= #{radius}",
:order => options[:order],
:limit => limit
}
end
##
# Query Google for geographic information about the given phrase.
# Returns the XML response as a hash. This method is not intended for
......
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