Comparison of NH₃(1, 1) excitation temperatures and spectra for a spherically symmetric cloud. Frame a shows the radial T_ex profiles computed with 1D versions of the Cppsimu and LOC programs and with the 3D version of LOC. The LOC runs use either a Cartesian grid with 64³ cells or the same with two additional levels of refinement. Frame b compares the spectra observed towards the centre of the model. A zoom into the peak of the main component is shown in the inset. The lower plots show the ratio of T_ex values (frame a) and the difference between the LOC and Cppsimu T_A values (frame b), with the colours listed in frame a.