nGC3 PCMs for a Gaia DR2 mock catalogue (with errors, extinction, and selection function) of test particles at r_gal between 13 and 14 kpc, for the flat disc (left) the Sine Lopsided warp (middle) and the S Lopsided warp (right). We note the asymmetry in the PCM signature of the SLop model, which is due to the stars lost in the I and IV quadrant when the effect of extinction and the selection function are included. The corresponding PCMs for the SineLop and SLop models without the effect of errors, extinction, and selection function is shown for comparison in Fig. D.5.