Left panels: three components (radial, azimuthal, and vertical, from top to bottom, respectively) of the Galactocentric velocity Median(V) as a function of and (X, Y with deconvolution correction according to Sect. 3.1). Application for Gaia-DR2 data including ν_r measurement with the constraints: |b|< 10°, . Inner green contour represents the region with error equal to 10, 10, and 2 km s⁻¹ for V_R, V_ϕ, and V_Z, respectively. Middle panels: error (in log scale) of V derived from the expansion in the formulae of as systematic error and the dispersion of values of ν_r, μ_ℓ, and μ_b divided by the root square of the number of points per bin as statistical errors. Right panels: rms value of V (corrected for measurement errors). Data of this figure are available at the CDS.