Rotation speed as a function of R for bins with |z| < 200 pc, adopting a solar azimuthal speed of V_g, ⊙ = 250 km s^-1 and an LSR azimuthal speed of V_c(R_⊙,z = 0) = 238 km s^-1. The dashed line is the weighted average of the bins without correction of systematic errors of the proper motion but taking into account the errors due to contamination of non-RCGs and including errors due to uncertainties in (U_⊙,V_g, ⊙,W_⊙). The solid line is the weighted average of the bins including the correction of systematic errors of the proper motion as explained in Sect. 5; error bars include statistical errors, uncertainties in (U_⊙,V_g, ⊙,W_⊙), errors due to contamination of non-RCGs and errors of systematic errors of proper motion (see Fig. 4).