Statistics of the along-track (AL) error plotted against the year of the observations. It incorporates several effects, including timing errors, uncertainties due to sizeand shape models (particularly relevant for single-chord events, which represent 61% of the total). Relevant features are the high dispersion before the late 90s, and the overall consistency afterwards. The AL error (two middle panels) is provided both in absolute values (mas) and in units of the asteroid radius. For reference the first rowrepeats the plot with the number of occultations for each year.