Correlation in the distribution of HISA and ¹³CO emission toward the six GMF regions as quantified by the projected Rayleigh statistic (V) in the HOG method (Soler et al. 2019). The panels present the computed spatial correlation between HISA and ¹³CO across velocities in terms of the projected Rayleigh statistic V for each filament region. The values of V are indicated by the color bar to the right of each panel. The white line in each panel shows the 1-to-1 correlation. The yellow contours show the 5σ threshold estimated from the Monte Carlo sampling. Large values of V indicate a high spatial correlation. Values of V close to zero indicate a random orientation of the HISA structures with respect to ¹³CO emission.