Method of updating a database of a navigation device and navigation device

To update a database of a navigation device which stores at least a base version of a digital map, versions of the digital map which are available locally in the database or remotely from the navigation device are identified. To execute the navigation task, a version of the digital map is selected for execution of the navigation task. Data from a sub-set of storage blocks in which the selected version is stored is required to execute the navigation task. Depending on whether all storage blocks of the sub-set are already stored locally in the database, data stored in storage blocks of the sub-set which are not yet stored locally in the database are downloaded via a wireless interface. The downloaded data are stored in the database without modifying the base version of the digital map.