The dat files are byte arrays of 0 and 1 in equirectangular projection (4320 x 2160) = 360 x 180.

  width = 4320
  nx = width
  ny = width/2

  mapz = bytarr(nx,ny)

      outfile = outdir+'/'+regions[i].id+'.dat'
      openw,1,outfile
      writeu,1,mapz
      close,1