Radially averaged Lorentz factor (top) and isotropic equivalent energy (bottom) of the jet head (see Sect. 2.3) as functions of Θ, at t − t_jet≃ 3 s. We compare the result for the original input data (dashed lines) with those obtained after a double spherical-to-Cartesian and Cartesian-to-spherical interpolation (continuous lines). We refer to the text for further details. Different colours refer to profiles for three different azimuthal angles Φ = 0° ,90° ,180° (in yellow, black, purple lines, respectively) and for the Φ-averaged result (blue line).