Region analyzed in this work, color coded according to different parameters as shown in the side color bar. Top: colors indicate the median of the total PM error of individual stars. Because of the combination of crowding and extinction, the error in the individual PM measurements is larger in the NSD region. Bottom: median PM error of each pixel is divided by the square root of the number of stars (minus one) in each pixel. This map shows the spatial trend of the errors on the mean and median PM, across the sky.