Top: distribution of the RV versus the longtitude ϕ₁ of all those common stars from LAMOST and DESI, which are represented by the red and magenta squares, respectively. Bottom: distributions of the tangential velocities V_T versus the longtitude ϕ₁ of all the member candidate stars with magnitude G < 18. The green lines and the errorbars represent the mean values and the dispersions of the two tangeltial velocities along the two directions ϕ₁ and ϕ₂ in each subsample with step of Δ_ϕ1 = 22°. The shadow regions represent the edges of the tangential velocities caused by the proper motion selection.