Four view ports of the SHAPE 3D mesh geometry model of I19312. The Free-Form view is the observer’s view with a position angle of −37°, where up is north and left is east. The modelled structures are composed of an inner spherical envelope (white), an outer elliptical envelope (green), and a pair of symmetric bipolar outflows (red). The solid lines on the upper-right panel are slits used to generate the position-velocity diagram shown in Fig. A.2.