docs: def lat_id(self, line):
          ''' Return the corresponding latitude
  
          Args:
              line (int): Line number
  
          Returns:
              Correponding latitude in degree
          '''
          if self.grid == 'WAC':
              lat = ((1 + self.LINE_PROJECTION_OFFSET - line) *
                     self.MAP_SCALE * 1e-3 / self.A_AXIS_RADIUS)
              return lat * 180 / np.pi
          else:
              lat = float(self.CENTER_LATITUDE) - \
                  (line - float(self.LINE_PROJECTION_OFFSET) - 1)\
                  / float(self.MAP_RESOLUTION)
              return lat