GeoKit on Rails

Geocoding with the Rails GeoKit Plugin
GeoKit official website
ym4r 提供了可以方便把google map 用的功能
而GeoKit 則是提供了許多 map application 會用到的功能, 例如 兩點之間的距離, 算某個範圍裡面的點等等

安裝
step1: 安裝plugincd [YOUR_RAILS_APP_ROOT] script/plugin install git://github.com/andre/geokit-rails.git

step2: 在environment, initializer 的 block 裡加上<br /> config.gem "geokit"

step3: 告訴rails 裝上這個gem<br /> rake gems:install

最後
在需要用到的controller 頂端 include GeoKit::Geocoders

---

把地址轉成經緯座標
<br />#controller <br />def show<br /> coordinates = GoogleGeocoder.geocode("台北縣OO市OOXX街123號")<br /> @map = GMap.new("map")<br /> @map.center_zoom_init([coordinates.lat, coordinates.lng], 14)<br />end<br />

---

自動轉經緯
如果你的table 裡有像lat, lng 的欄位, 在生成store object 時, 便會自動去算你設定為地址的欄位, 把對應的經緯填入
<br />class Store < ActiveRecord::Base<br /> acts_as_mappable :auto_geocode =>{:field => :street_address}<br />end <br />

---

算點跟點之間的距離
<br />#controller <br />def show<br /> coordinates1 = GoogleGeocoder.geocode("台北縣OO市OOXX街123號")<br /> coordinates2 = GoogleGeocoder.geocode("台南縣OO市OOXX街123號")<br /><br /> #除了可以利用物件算之外<br /> @distance = coordinates1.distance_from(coordinates2)<br /><br /> #還可以直接丟座標<br /> @distance = Store.distance_between([lat,lng], [lat2,lng2])<br />end<br />

---

找到某個範圍之內所有的點
<br />city = GoogleGeocoder.geocode("Youngstown, Ohio")<br />pizzerias = Pizzeria.find(:all, :origin => [city.lat, city.lng],<br /> :within => 25)<br />

---

從使用者ip判斷位置
<br />def ip<br /> @user_location = IpGeocoder.geocode(request.remote_ip)<br />end<br />

## USING INCLUDES

You can use includes along with your distance finders:

stores=Store.find :all, :origin=>home, :include=>[:reviews,:cities] :within=>5, :order=>'distance'

However, ActiveRecord drops the calculated distance column when you use include. So, if you need to use the distance column, you‘ll have to re-calculate it post-query in Ruby:

stores.sort_by_distance_from(home)

In this case, you may want to just use the bounding box condition alone in your SQL (there‘s no use calculating the distance twice):
<br /> bounds=Bounds.from_point_and_radius(home,5)<br /> stores=Store.find :all, :include=>[:reviews,:cities] :bounds=>bounds<br /> stores.sort_by_distance_from(home)<br />