Example of a tile with CO emission structures mostly parallel to the Galactic plane, as identified by the highest V values in the left panel of Fig. 2. The top panels show the ¹²CO(1–0) line emission at 7.^′5 FWHM resolution in the Dame et al. (2001) composite survey. The bottom panels show the ¹²CO(1–0) line emission at 55^′′ FWHM resolution in the MWISP survey toward the region marked with the green square in the top panel. The left, middle, and right panels show the line emission map, its gradient, and the filamentary structures identified by the second eigenvalue of the Hessian matrix (Eq. (2)) respectively.