Filament intrinsic polarization angle along (left panel), and perpendicular (right panel) to, the crests of the filaments. The crosses are data points computed from Q and U values, after averaging the background subtracted maps in the direction perpendicular (left panel) and parallel (right) to the filament crests. In the left panel, x is a coordinate along the filament crest, while in the right panel, r is the radial distance to the filament crests. In the right panel, the dashed line represents the background polarization angle. The beam is 0.3 pc for Musca, and 0.2 pc for B211 and L1506.