code: def _get_sector(self, channel, nlines, ncols):
          
          if self._is_vis(channel):
              margin = 100
              sectors_ref = self.vis_sectors
          else:
              margin = 50
              sectors_ref = self.ir_sectors
  
          for (nlines_ref, ncols_ref), sector in sectors_ref.items():
              if np.fabs(ncols - ncols_ref) < margin and \
                      np.fabs(nlines - nlines_ref) < margin:
                  return sector
  
          return UNKNOWN_SECTOR
docs: Determine which sector was scanned