From: Chris Winslett <christopherwinslett@...>
Date: 2006-04-14T06:25:43+09:00
Subject: Metar Weather Grabber

I don't want to pay money to get weather feeds from a bunch of different 
countries.  So I took my hand at writing my own.  It is for an ajax 
service that grabs the XML.

If you use this, expand on it.  If you expand on it, post it back on 
here.  There are somethings I haven't gotten to yet.  The usage of the 
weather codes needs to get better too.

#!/usr/bin/ruby

require 'rexml/document'
require 'open-uri'
require 'pp'

include REXML

class Weather
  attr_reader :wind, :temperature, :dew_point, :sky, :sky_icon

  def initialize(metar_string)
    @metar_string = metar_string
    @wind = self.set_wind()
    @temperature, @dew_point = self.set_temperature()
    @sky, @sky_icon = self.set_sky()
  end

  def set_wind
    sample_string = $& if @metar_string =~ 
/(\d{3}|VRB)[G]{0,1}\d{1,4}KT/

    direction = self.get_cardinal_direction(sample_string[0...3])
    speed = 
sample_string[sample_string.rindex(/\d{1,4}KT/)..sample_string.length-3].to_i

    "#{direction} at #{speed}mph"
  end

  def get_cardinal_direction(degrees)
    case degrees.to_i
    when 0:    "Variable"
    when 1..4:      "N"
    when 5..35:     "NNE"
    when 36..55:    "NE"
    when 56..85:    "ENE"
    when 86..95:    "E"
    when 96..125:   "ESE"
    when 126..135:  "SE"
    when 136..175:  "SSE"
    when 176..185:  "S"
    when 185..215:  "SSW"
    when 216..225:  "W"
    when 226..265:  "WSW"
    when 265..275:  "W"
    when 275..295:  "WNW"
    when 296..305:  "NW"
    when 306..346:  "NNW"
    when 347..370:  "N"
    else		 "Gusty"
    end
  end

  def set_temperature
    sample_string = $&.strip if @metar_string =~  / 
[M]{0,1}\d{2}\/[M]{0,1}\d{2} /

    celcius    = sample_string[0..2].to_i
    fahrenheit = ( ( celcius.to_i * 9 ) / 5 + 32 )

    dew_point_celcius       = 
sample_string[3..sample_string.length-1].to_i
    dew_point_fahrenheit    = ( ( dew_point_celcius * 9 ) / 5 + 32)

    ["#{fahrenheit} F (#{celcius} C)", "#{dew_point_fahrenheit} F 
(#{dew_point_celcius} C)"]
  end

  def set_sky
    sky = $&.strip if @metar_string =~ 
/(SKC|FEW|SCT|BKN|OVC|CLR)[CB]{0,1}/
    sky = $&.strip if @metar_string =~ 
/(RA|DZ|SN|GR|SQ|GS|SG|IC|PE|BR|FG|FU|HZ|VA|DU|SA|SS|DS|FC|MI|BC|DR|BL|SH|TS|FZ)\+{1}/

    weather_codes = {	"SKC"=> ["Scattered Clouds", 30],
			"FEW"=> ["Sunny"           , 32],
			"SCT"=> ["Partly Cloudy"   , 29],
			"BKN"=> ["Mostly Cloudy"   , 28],
			"OVC"=> ["Overcast"        , 26],
			"CLR"=> ["Sunny"           , 32],
			"RA"=> ["Raining"          , 40],
			"DZ"=> ["Drizzle"          , 39],
			"SN"=> ["Snow"             , 16],
			"GR"=> ["Hail"             , 35],
			"SQ"=> ["Squalls"          , nil],
			"GS"=> ["Small Hail"       , 35],
			"SG"=> ["Snow Grains"      , 15],
			"IC"=> ["Diamond Dust"     , nil],
			"PE"=> ["Ice Pellets"      , nil],
			"BR"=> ["Mist"             , nil],
			"FG"=> ["Fog"              , 20],
			"FU"=> ["Smoke"            , 22],
			"HZ"=> ["Haze"             , 21],
			"VA"=> ["Volcanic Ash"     , nil],
			"DU"=> ["Widespead dust"   , nil],
			"SA"=> ["Sand"             , nil],
			"SS"=> ["Sandstorm"        , nil],
			"DS"=> ["Duststorm"        , nil],
			"FC"=> ["Funnel Cloud"     , nil],
			"MI"=> ["Shallow"          , nil],
			"BC"=> ["Patches"          , nil],
			"DR"=> ["Drifting"         , nil],
			"BL"=> ["Blowing"          , nil],
			"SH"=> ["Showers"          , nil],
			"TS"=> ["Thunderstorm"     , 1],
			"FZ"=> ["Supercooled(Freezing)", nil],
			"+" => ["Heavy"            , nil],
			"TCU"=> ["Towering Cumulonimbs", nil]
                     }
    icon = ''
    weather_codes.each do | code, description |
      sky = sky.gsub(code, description[0])
      icon = description[1] if !description[1].nil?
    end

    [sky, icon]
  end
end

# Set up the XML document
xml_write = REXML::Document.new('<return><method/><result/></return>')
xml_write.elements["//method"].text = "updateWeather"

#Array of Cities and Local from the Weather xml information
cities_url = {"New York, NY"   => 
"ftp://weather.noaa.gov/data/observations/metar/stations/KLGA.TXT",
             "London, UK"     => 
"ftp://weather.noaa.gov/data/observations/metar/stations/EGLL.TXT"}

cities_url.each do |location, url|

  current_weather = Element.new()
  current_weather.add_element("CurrentWeather")
  current_weather.elements["//CurrentWeather"].add_attribute("label", 
location)

  element_write = 
current_weather.elements["//CurrentWeather[@label='"+location+"']"]

  metar   = Document.new(open(url))
  weather = Weather.new(metar.to_s.gsub("\n", " "))

  element_write.add_element("DewPoint").text          = 
weather.dew_point
  element_write.add_element("Temperature").text       = 
weather.temperature
  element_write.add_element("Wind").text              = weather.wind
  element_write.add_element("SkyConditions").text     = weather.sky
  element_write.add_element("SkyConditionsIcon").text = weather.sky_icon
  element_write.add_element("RelativeHumidity").text  = metar[0]
  xml_write.elements["//result"].add_element(current_weather.elements["//CurrentWeather"])
end

xml_writable = File.new("public_html/weather.xml", "w+")
xml_write.write(xml_writable, -1, true)

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