Calculate the distance between 2 points in km

gistfile1.coffee

class Geo

  @radiusInMiles: 3956.0
  @radiusInKilometers: 6367.0
  
  @toRadian: (v) ->
    v * (Math.PI / 180)
    
  @diffRadian: (v1, v2) ->
    @toRadian(v2) - @toRadian(v1)
    
  # Calculate the distance between 2 points in km
  # http://pietschsoft.com/post/2008/02/Calculate-Distance-Between-Geocodes-in-C-and-JavaScript.aspx
  @calcDistance: (lat1, lng1, lat2, lng2, radius) ->
    radius * 2 * Math.asin( Math.min(1, Math.sqrt( ( Math.pow(Math.sin((@diffRadian(lat1, lat2)) / 2.0), 2.0) + Math.cos(@toRadian(lat1)) * Math.cos(@toRadian(lat2)) * Math.pow(Math.sin((@diffRadian(lng1, lng2)) / 2.0), 2.0) ) ) ) )

  @distanceKmFormatted: (lat1, lng1, lat2, lng2) ->
    distance = @calcDistance(lat1, lng1, lat2, lng2, @radiusInKilometers)
    distance.toFixed(2) + " km"