Top: schematic view of a thin wind annulus of radius r_j, expansion velocity V_r, azimuthal velocity V_ϕ, and vertical velocity V_z along the jet axis, inclined by an angle i from the line of sight. A point on this annulus is located by the azimuthal angle ϕ. Bottom: the transverse PV diagram for the wind annulus is an ellipse (in black) centered on r_proj = 0 and V_rad = − cosiV_z, of minor andmajor axes and tilt angle Θ given by Eqs. B.8 and B.9. Three pairs of points of interest are indicated: the on-axis points (in green) giving the projected V_r ; the points of maximum radii (in blue) giving the projected V_ϕ; and the points of maximum radial velocity (in red) with and , where intensity peaks are located at high spectral resolution (see Appendix B.2 and Fig. B.2).