function save_ballgt( gt_file, gt_m );

  fid = fopen( gt_file, 'wt' );
  if fid < 0
    error( [ mfilename ' could not write-open "' gt_file '"' ] );
  else
    fprintf( fid,'%4d %4d %4.1f %10.4f %10.4f %10.4f %10.4f\n',gt_m.');
    fclose( fid );
  end