Schematic illustration of the wind model composed of a central point source (orange) and a bipolar outflow with the radius R_o (red). The central source emits Lyα photons, following a Gaussian profile with a width σ_Src. The bipolar outflow is characterized by the H I column density N_H I, the opening angle θ_o, Wind (increasing from the +z-axis, as the blue solid arrow), and the expansion velocity v_exp parameters. The inner radius of the outflow R_i is fixed at 0.1 R_o. As the wind model is symmetric about the z-axis, the line of sight angle θ_LOS is the angle from the +z-axis following the orange arrow, and thus with θ_LOS = 0° meaning observing in the direction of the outflow, and θ_LOS = 90° representing the equatorial view.