Excitation diagram of the different tracers observed in NGC 7023 after dilution correction (red squares) and the best fit model (black, P_th = 10⁸ K cm⁻³, = 10, global scaling factor = 0.7). The best model has been chosen to optimise the fitting of the ¹²CO (high-J lines), H₂ and CH⁺ lines only. In the last panel, the intensity values are normalised by the mean observed value for each line. The grey lines show the obtained variability when the thermal pressure is divided (dashed lines) or multiplied (plain lines) by a factor of 1.5. The best value for the scaling factor was found to be 1.2 for the model at P_th/1.5 and 0.47 for the model at P_th × 1.5.