Sketch demonstrating quantities used in the analysis. The red and the blue ellipses denote 1σ positional uncertainty of a source in VLBI and Gaia DR3 data, respectively. The green vector represents the parsec-scale jet direction. ψ is the angle between the jet direction and the VGD vector. σ_ψ is the estimate of uncertainty of ψ, calculated as the angle between maximum and minimum ψ consistently with the error ellipses.