This document contains code for a web application that serves geographic vector data stored in a Postgres database. It includes code to: 1) Connect to a Postgres database and import vector data from a shapefile into a table with a geometry column. 2) Define routes in a Sinatra application to serve pre-rendered web pages with the vector data visualized using SVG and embedded in HTML. 3) Include JavaScript code to pan and zoom the vector data visualization in the browser.

12. http://en.wikipedia.org/wiki/
File:Bundesarchiv_Bild_102-08759,_Flugzeug_Junkers_G-24.jpg
Attribution: Bundesarchiv, Bild 102-08759 / Unknown / CC-BY-SA

20. No. 386

43. $KCODE = 'u'
require 'rubygems'
require 'sequel'
require 'geo_ruby'
DB = Sequel::connect('postgres://fitter:happier@localhost/more_productive',
:encoding => 'UTF-8')
DB.create_table!(:japan_highway) do
primary_key :gid
String :type
String :name
boolean :oneway
real :lanes
end
DB["SELECT AddGeometryColumn('', 'japan_highway', 'the_geom', '4326', 'MULTILINESTRING', 2);"].first
DB.transaction {
GeoRuby::Shp4r::ShpFile.open('japan_highway.shp') {|shp|
shp.each {|r|
DB[:japan_highway].insert({
:type => r.data['TYPE'],
:name => r.data['NAME'],
:oneway => r.data['ONEWAY'] == 'yes',
:lanes => r.data['LANES'].to_f,
:the_geom => :ST_GeomFromText.sql_function(r.geometry.as_wkt, 4326)
})
}
}
}

44. class App < Sinatra::Base
DB = Sequel::connect('postgres://fitter:happier@localhost/more_productive')
get '/geohash/:file_name' do
content_type 'text/html'
geohash = params[:file_name].sub('.html', '')
extent = GeoHash.decode(geohash)
...
bbox = "ST_GeomFromText('POLYGON ((#{lng0} #{lat0}, #{lng1} #{lat0}, #{lng1} #{lat1}, #{lng0} #{lat1}, #{lng0} #{lat0}))', 4326)"
@dataset = DB["SELECT ST_AsSVG(ST_Affine(ST_Intersection(the_geom, #{bbox}), #{a}, #{b}, #{d}, #{e}, #{x_off}, #{y_off}), 0, 0),
type, name FROM japan_highway WHERE ST_Intersects(the_geom, #{bbox});"]
instr = []
@dataset.each {|r|
instr << " r.path('#{r[:st_assvg]}').attr('stroke', '#{color}');n"
}
s = haml <<-EOS
!!!XML
%html
...
%body
:javascript
window.onload = function() {
...
});
window.document.addEventListener('touchstart', function(evt) {
...
}, false);
...
}
EOS
File.open("public/geohash/#{geohash}.html", 'w') {|w|
w.print s
}
s
end
end
App.run! :port => 2010

45. require 'app'
run Sinatra::Application
require 'rubygems'
require 'sinatra'
get '/' do
redirect '/geohash/xn77n.html'
end
require 'rubygems'
require 'pr_geohash'
require 'open-uri'
ALPHABET = "0123456789bcdefghjkmnpqrstuvwxyz"
def get(geohash)
url = "http://localhost:2010/geohash/#{geohash}.html"
print url, "n"
open url
end
%w{xn7 xnk}.each {|seed|
ALPHABET.each_char {|c1|
ALPHABET.each_char {|c2|
get(seed + c1 + c2)
}
}
}
$ sudo gem install heroku
$ heroku create degree-zero-web-mapping
$ git init
$ git add .
$ git commit
$ git push heroku master

47. Demo