Rotation diagram of metastable ammonia transitions toward NGC 1068 (see Sect. 3.2). The open squares show the normalized column densities determined from the integrated line intensities. The numbers mark the rotational temperatures in K. The absolute calibration uncertainties, including the dominant contribution from the baseline fits as well as uncertainties in the Gaussian fits and in the overall calibration uncertainty, have been taken as error bars (Sect. 2). Note, however, that relative calibration is excellent up to at least the (4,4) transition.