The invention concerns a process for updating map data of a navigation system in a vehicle, wherein the navigation system includes a digital map of a road and path network as well as a digital supplemental map, wherein in the digital supplemental map data supplemental to the road and path network are stored. The process includes the steps: a) producing differential data for an updated digital map, using the digital map, b) replacing the digital map in the vehicle with the updated digital map, c) updating the digital supplemental map in the vehicle using the differential data.