1. A computer-implemented method for route calculation, the method comprising: at a navigation system, receiving a destination; the navigation system calculating a route from a current position to the destination, wherein the route is a sequence of road segments; retrieving data indicative of a geographic position for at least one road segment from a geographic database associated with the navigation system; retrieving a distribution function for an attribute describing the at least one road segment from the geographic database associated with the navigation system, wherein the attribute is different than the geographic position, wherein the distribution function represents uncertainty that the attribute is accurate; and providing an output that includes information about the uncertainty in the route.