All-sky maps characterizing the astrometric performance of the nominal TGAS solution (pixel size 3.4 deg²). The cyan line denotes the ecliptic. a) Actual errors in parallax (TGAS solution minus simulated true values), median per pixel to show that the solution is unbiased. b) Same as before, but RSE per pixel to characterize the size of the actual errors. c) Formal standard errors in parallax as computed in the astrometric solution. d) RSE values of the normalized errors in parallax.