Measurement of phase angle for phase spirals at different azimuthal angles of guiding centre θ_ϕ. Top panel: rotation angle of the phase spirals as functions of θ_ϕ for stars in the solar neighbourhood (d < 1 kpc). Each point uses data from ±3.5°. The zero point of the spiral angle is arbitrary. Bottom panel: difference in the angle of the arms of the phase spiral. The trend is fitted with a line.