Circular statistics used for the study of the orientation of the HI filamentary structures found using the Hessian and the RHT methods across velocity channels toward the region presented in Fig. C.2. Top: mean resulting vector (r), which indicates if the distribution of orientation angles is flat (r ≈ 0) or sharply unimodal (r ≈ 1). Middle: projected Rayleigh statistic (V), which indicates if the distribution of orientation angles is clearly peaked around 0° (V ≫ 0) or 90° (V ≪ 0). Bottom: mean orientation angle () of the HI filamentary structures.