code: def get_area_def(self, dsid):
          
          cfac = np.int32(self.mda['cfac'])
          lfac = np.int32(self.mda['lfac'])
          coff = np.float32(self.mda['coff'])
          loff = np.float32(self.mda['loff'])
  
          a = self.mda['projection_parameters']['a']
          b = self.mda['projection_parameters']['b']
          h = self.mda['projection_parameters']['h']
          lon_0 = self.mda['projection_parameters']['SSP_longitude']
          nlines = int(self.mda['number_of_lines'])
          ncols = int(self.mda['number_of_columns'])
  
          area_extent = self.get_area_extent((nlines, ncols),
                                             (loff, coff),
                                             (lfac, cfac),
                                             h)
  
          proj_dict = {'a': float(a),
                       'b': float(b),
                       'lon_0': float(lon_0),
                       'h': float(h),
                       'proj': 'geos',
                       'units': 'm'}
  
          area = geometry.AreaDefinition(
              'some_area_name',
              "On-the-fly area",
              'geosmsg',
              proj_dict,
              ncols,
              nlines,
              area_extent)
  
          self.area = area
          return area
docs: Get the area definition of the band.