Shape of the phase-space spiral, represented as a one-dimensional line in the (z, w)-plane, when biased by faulty radial velocity assignments. The dashed blue and orange lines show the spiral when radial velocity assignment is biased by ±10 km s⁻¹, assuming that the spiral is observed at a distance of . The spiral is plotted for vertical energies in range E_z ∈ [Φ(250 pc),Φ(800 pc)]. The plus sign marks the origin of the (z, w)-plane.