code: def parse_file_name_starting_position(self):
          
          groups = mod_re.findall('([NS])(\d+)([EW])(\d+)\.hgt', self.file_name)
  
          assert groups and len(groups) == 1 and len(groups[0]) == 4, 'Invalid file name {0}'.format(self.file_name)
  
          groups = groups[0]
  
          if groups[0] == 'N':
              latitude = float(groups[1])
          else:
              latitude = - float(groups[1])
  
          if groups[2] == 'E':
              longitude = float(groups[3])
          else:
              longitude = - float(groups[3])
  
          self.latitude = latitude
          self.longitude = longitude
docs: Returns (latitude, longitude) of lower left point of the file