Summary statistics for the 2 million sources in the primary data set. The five maps along the main diagonal show, from top-left to bottom-right, the standard uncertainties in α, δ, ϖ, μ_{α ∗}, μ_δ. The ten maps above the diagonal show the correlation coefficients, in the range −1 to + 1, between the corresponding parameters on the main diagonal. All maps use an Aitoff projection in equatorial (ICRS) coordinates, with origin α = δ = 0 at the centre and α increasing from right to left. Median values are shown in cells of about 0.84 deg².