An apparatus includes a map data storage device, a map update device, a determination device, and a data production device. The storage device stores map data. The update device reflects a first map update to a first version of the map data to produce a second version of the map data when the first map update occurs. The update device reflects a second map update to the second version of the map data to produce a third version of the map data when the second map update occurs after the first map update. The determination device determines whether the first and second map updates depend on each other. The production device produces map differential data from the first and second map updates when the determination device determines that the first and second map updates depend on each other.