Polarization angle profile as a function of Galactic longitude. The mean polarization angle is computed from longitudes between −7.5° and 7.5° and latitudes between −0.15° and 0.15° in 100 boxes of size 0.15° in longitude. The longitude profiles are shown for the Planck 143, 217 and 353 GHz channels (blue, orange and red, respectively) and PILOT (black). The error bars represent the standard deviation of the angle in each boxes.