Position-velocity slice along the major axis of NGC 3198 (1′≃4.2 kpc at the distance adopted). The white area shows the emission from the thin H I disc (internal mask), derived as discussed in Sect. 2.2. The region outside the green dashed contour (external mask) is not associated to the galaxy and is set to zero in the data. The orange squares show the rotation curve derived with ^3DBAROLO. Black contours are spaced by powers of 2, the outermost being at an intensity level of 0.28 mJy beam⁻¹ (2σ_noise). A negative contour (−2σ_noise) is shown as a dashed grey contour.