Distribution of the mean radial velocity (⟨V_R⟩) in the (x − y)-plane, calculated at t = 9 Gyr for the model rthick0.0, with the bar placed at different viewing angles with respect to a hypothetical observer (shown in diamond) at a solar-like position (R = −8 kpc, ϕ = 0°, z = 0). The cyan circles in each sub-panel denote the variation in the phase-angle of the m = 4 Fourier coefficient (φ₄), computed from the distribution of ⟨V_R⟩. The dashed straight line denotes the ‘true’ bar angle, computed from the intrinsic density distribution of the stellar particles.