A method comprising receiving probe data indicative of a set of navigational signal measurements that is matched to a link segment, determining a set of measurement errors such that each measurement error of the set of measurement errors is a difference between a location indicated by the link segment and a location indicated by a navigational signal measurement of the set of navigational signal measurements, determining at least one statistical attribute of the set of measurement errors, and storing an indication of the statistical attribute in map information associated with the link segment is disclosed.