code: def tilenums2latlon(xtile, ytile, zoom)
        factor = 2.0 ** zoom
        lon = (xtile * 360 / factor) - 180.0
        lat = Math.atan(Math.sinh(Math::PI * (1 - 2 * ytile / factor)))
        return Point.new(degrees(lat), lon)
      end
docs: Convert tile coordinates pair to latitude, longitude. Returns latitude, longitude as a CloudMade::Point object
   * +xtile+ X coordinate of the tile
   * +ytile+ Y coordinate of the tile
   * +zoom+ Zoom level