1. A method for updating certain attribute specifications for road segments in digital maps, such as posted speed limits, taxi stops, road geometries or POI information, by extrapolating probe data from a profiled subset of trustworthy probe traces, said method comprising the steps of: providing a digital map having at least first and second road segments, each of the road segments having a common attribute with a respective attribute specification, the specification for the first road segment attribute being reliably known and the specification for the second road segment attribute being unknown or unreliable; reporting data from a plurality of probes tracking across both of the first and second road segments, the reported data including attribute information; matching each probe trace to a specific road segment in the digital map for a given time while collecting its reported attribute information; calculating a correspondence value between the known attribute specification of the first road segment and the reported attribute information for each probe trace matched to the first road segment; defining a correspondence threshold for the attribute specification; identifying from among the plurality of probe traces matched to the first road segment a subset of trustworthy probe traces whose calculated correspondence value does not exceed the correspondence threshold; collecting the reported attribute information from each trustworthy probe trace when matched to the second road segment; extrapolating an attribute specification for the second road segment based on the collected attribute information from all of the trustworthy probe traces when matched to the second road segment; and updating the digital map by setting the attribute specification for the second road segment in relation to the extrapolated attribute specification.