code: def getTile(self, lat, lon):
          
          global childFileListDownload
          if childFileListDownload is not None and childFileListDownload.is_alive():
              '''print "Getting file list"'''
              return 0
          elif not self.filelist:
              '''print "Filelist download complete, loading data"'''
              data = open(self.filelist_file, 'rb')
              self.filelist = pickle.load(data)
              data.close()
  
          try:
              continent, filename = self.filelist[(int(lat), int(lon))]
          except KeyError:
              '''print "here??"'''
              if len(self.filelist) > self.min_filelist_len:
                  # we appear to have a full filelist - this must be ocean
                  return SRTMOceanTile(int(lat), int(lon))
              return 0
  
          global childTileDownload
          if not os.path.exists(os.path.join(self.cachedir, filename)):
              if childTileDownload is None or not childTileDownload.is_alive():
                  try:
                      childTileDownload = multiprocessing.Process(target=self.downloadTile, args=(str(continent), str(filename)))
                      childTileDownload.start()
                  except Exception as ex:
                      childTileDownload = None
                      return 0
                  '''print "Getting Tile"'''
              return 0
          elif childTileDownload is not None and childTileDownload.is_alive():
              '''print "Still Getting Tile"'''
              return 0
          # TODO: Currently we create a new tile object each time.
          # Caching is required for improved performance.
          try:
              return SRTMTile(os.path.join(self.cachedir, filename), int(lat), int(lon))
          except InvalidTileError:
              return 0
docs: Get a SRTM tile object. This function can return either an SRTM1 or
              SRTM3 object depending on what is available, however currently it
              only returns SRTM3 objects.